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•  2IR.G.KIIELLER  I 


THE 

LIFE 

OF 

SIR    ISAAC    NEWTON 

BY 

DAVID  BREWSTER,  LL.D.  F.R.S. 


Ergo  vivida  vis  anim?  pervicit,  et  extra 

Processit  longe  flamnwntia  moenia  mundi ; 

Atque  omoe  immensum  peragravit  meote  animoque. 

Lttcret.  lib.  i.  1.  731 


The  Birthplace  of  Ncwtoa. 

NEW-YORK: 

PUBLISHED   BY   HARPER   &   BROTHERS, 

NO.   82  C  L  I  F  F-S  T  R  E  K  T. 

1840. 


TO 

THE   RIGHT   HONOURABLE 

LORD    BRAYBROOKE. 


THE  kindness  with  which  your  lordship  intrusted 
to  me  some  very  valuable  materials  for  the  compo- 
sition of  this  volume  has  induced  me  to  embrace  the 
present  opportunity  of  publicly  acknowledging  it. 
But  even  if  this  personal  obligation  had  been  less 
powerful,  those  literary  attainments  and  that  en- 
lightened benevolence  which  reflect  upon  rank  its 
highest  lustre  would  have  justified  me  in  seeking 
for  it  the  patronage  of  a  name  which  they  have  so 
justly  honoured* 

DAVID  BREWSTER. 

Allerly,  June  1st,  1831. 


A/767/7 


PREFACE. 


As  this  is  the  only  Life  of  Sir  Isaac  Newton  on 
any  considerable  scale  that  has  yet  appeared,  I 
have  experienced  great  difficulty  in  preparing  it  for 
the  public.  The  materials  collected  by  preceding 
biographers  were  extremely  scanty ;  the  particulars 
of  his  early  life,  and  even  the  historical  details  of 
his  discoveries,  have  been  less  perfectly  preserved 
than  those  of  his  illustrious  predecessors  ;  and  it  is 
not  creditable  to  his  disciples  that  they  have  allowed 
a  whole  century  to  elapse  without  any  suitable 
record  of  the  life  and  labours  of  a  master  who 
united  every  claim  to  their  affection  and  gratitude. 

In  drawing  up  this  volume,  I  have  obtained  much 
assistance  from  the  account  of  Sir  Isaac  Newton  in 
the  Biographia  Britannica ;  from  the  letters  to  Ol- 
denburg, arid  other  papers  in  Bishop  Horsley's 
edition  of  his  works ;  from  Tumor's  Collections  for 
the  History  of  the  Town  and  Soke  of  Grantham ; 
from  M.  Biot's  excellent  Life  of  Newton  in  the 
Biographic  Universelle ;  and  from  Lord  King's  Life 
and  Correspondence  of  Locke. 

Although  these  works  contain  much  important 
information  respecting  the  Life  of  Newton,  yet  I 
have  been  so  fortunate  as  to  obtain  many  new  ma- 
terials  of  considerable  value. 


10  PREFACE. 

To  the  kindness  of  Lord  Braybrooke  I  have  been 
indebted  for  the  interesting  correspondence  of  New- 
ton, Mr.  Pepys,  and  Mr.  Millington,  which  is  now 
published  for  the  first  time,  and  which  throws  much 
light  upon  an  event  in  the  life  of  our  author  that 
has  recently  acquired  an  unexpected  and  a  painful 
importance.  These  letters,  when  combined  with 
those  which  passed  between  Newton  and  Locke, 
and  with  a  curious  extract  from  the  manuscript  diary 
of  Mr.  Abraham  Pryme,  kindly  furnished  to  me  by 
his  collateral  descendant  Professor  Pryme  of  Cam- 
bridge, fill  up  a  blank  in  his  history,  and  have  ena- 
bled me  to  delineate  in  its  true  character  that  tem- 
porary indisposition  which,  from  the  view  that  has 
been  taken  of  it  by  foreign  philosophers,  has  been 
the  occasion  of  such  deep  distress  to  the  friends  of 
science  and  religion. 

To  Professor  Whewell,  of  Cambridge,  I  owe  very 
great  obligations  for  much  valuable  information. 
Professor  Rigaud,  of  Oxford,  to  whose  kindness  I 
have  on  many  other  occasions  been  indebted,  sup 
plied  me  with  several  important  facts,  and  with  ex 
tracts  from  the  diary  of  Hearne  in  the  Bodleian 
Library,  and  from  the  original  correspondence  be- 
tween Newton  and  Flamstead,  which  the  president 
of  Corpus  Christi  College  had  for  this  purpose  com- 
mitted to  his  care ;  and  Dr.  J.  C.  Gregory,  of  Edin- 
burgh, the  descendant  of  the  illustrious  inventor  of 
the  reflecting  telescope,  allowed  me  to  use  his  un- 
published account  of  an  autograph  manuscript  of 
Sir  Isaac  Newton,  which  was  found  among  the  pa- 
pers of  David  Gregory,  Savilian  Professor  of  As- 
tronomy at  Oxford,  and  which  throws  some  light  on 
the  history  of  the  Principia. 


PREFACE.  11 

I  have  been  indebted  to  many  other  friends  for 
the  communication  of  books  and  facts,  but  espe- 
cially to  Sir  William  Hamilton,  Bart.,  whose  libe- 
rality in  promoting  literary  inquiry  is  not  limited  to 
the  circle  of  his  friends. 

D.B. 

Alhrly,  June  1st,  1831. 


CONTENTS. 


CHAPTER  I.  Pag» 

The  Pre-eminence  of  Sir  Isaac  Newton's  Reputation — The  Interest 
attached  to  the  Study  of  his  Life  and  Writings — His  Birth  and 
Parentage — His  e^rly  Education— Is  sent  to  Grantham  School— 
His  early  Attachment  to  Mechanical  Pursuits — His  Windmill — 
His  Water-clock— His  Self-moving  Cart— His  Sun-dials— His 
Preparation  for  the  University H 

CHAPTER  II. 

Newton  enters  Trinity  College,  Cambridge — Origin  of  his  Propen- 
sity for  Mathematics — He  studies  the  Geometry  of  Descartes  unas- 
sisted— Purchases  a  Prism — Revises  Dr.  Barrow's  Optical  Lec- 
tures— Dr.  Barrow's  Opinion  respecting  Colours — Takes  his  De- 
grees— Is  appointed  a  Fellow  of  Trinity  College — Succeeds  Dr. 
Barrow  in  the  Lucasian  Chair  of  Mathematics 26 

CHAPTER  III. 

Newton  occupied  in  grinding  Hyperbolical  Lenses— His  first  Ex- 
periments with  the  Prism  made  in  1666 — He  discovers  the  Com- 
position of  White  Light,  and  the  different  Refrangibility  of  the 
Rays  which  compose  it — Abandons  his  Attempts  to  improve  Re- 
fracting Telescopes,  and  resolves  to  attempt  the  Construction  of 
Reflecting  ones — He  quits  Cambridge  on  account  of  the  Plague — 
Constructs  two  Reflecting  Telescopes  in  1668,  the  first  ever  exe- 
cuted—One of  them  examined  by  the  Royal  Society,  and  shown 
to  the  King — He  constructs  a  Telescope  with  Glass  Specula — Re- 
eent  History  of  the  Reflecting  Telescope — Mr.  Airy's  Glass  Specula 
—Hadley's  Reflecting  Telascopes—  Short's— Berschel's— -Ram- 
age*s — Lord  Oxmantown's 30 

CHAPTER  IV. 

He  delivers  a  Course  of  Optical  Lectures  at  Cambridge— Is  elected 
Fellow  of  the  Royal  Society — He  communicates  to  them  his  Dis- 
coveries on  the  different  Refrangibility  and  Nature  of  Light- 
Popular  Account  of  them— They  involve  him  in  various  Contro- 
versies—His Dispute  with  Pardies— Linus— Lucas— Dr.  Hooke 

.  and  Mr.  Huygens — The  Influence  of  these  Disputes  on  the  mind 
of  Newton 47 

CHAPTER  V. 
Mistake  of  Newton  in  supposing  that  the  Improvement  of  Befraot- 

B 


14  CONTENTS. 

Pag» 

ing  Telescopes  was  hopeless — Mr.  Hall  invents  the  Achromatic 
Telescope— Principles  of  the  Achromatic  Telescope  explained— It 
is  reinvented  by  Dollond,  and  improved  by  future  Artists — Dr. 
Blair's  Aplanatic  Telescope — Mistakes  in  Newton's  Analysis  of 
the  Spectrum — Modern  Discoveries  respecting  the  Structure  of 
the  Spectrum 63 

CHAPTER  VI. 

Colours  of  thin  Plates  first  studied  by  Boyle  and  Hooke— Newton 
determines  the  Law  of  their  Production — His  Theory  of  Fits  of 
easy  Reflection  and  Transmission— Colours  of  thick  Plates 75 

CHAPTER  VII. 

Newton's  Theory  of  the  Colours  of  Natural  Bodies  explained — Ob- 
jections to  it  stated — New  Classification  of  Colours—  Outline  of  a 
new  Theory  proposed 89 

CHAPTER  VIII. 

Newton's  Discoveries  respecting  the  Inflection  or  Diffraction  of 
Light — Previous  Discoveries  of  Grimaldi  and  Dr.  Hooke — Labours 
of  succeeding  Philosophers— Law  of  Interference  of  Dr.  Young— 
Fresnel's  Discoveries —New  Theory  of  Inflection  on  the  Hypothe- 
sis of  the  Materiality  of  Light  99 

CHAPTER  IX. 

Miscellaneous  Optical  Researches  of  Newton — His  Experiments  on 
Refraction— His  Conjecture  respecting  the  Inflammability  of  the 
Diamond— His  Law  of  Double  Refraction— His  Observations  on 
the  Polarization  of  Light— Newton's  Theory  of  Light— His  "  Op- 
tics"   106 

CHAPTER  X. 

Astronomical  Discoveries  of  Newton— Necessity  of  combined  Exer 
tion  to  the  completion  of  great  Discoveries — Sketch  of  the  History 
of  Astronomy  prexrfous  to  the  time  of  Newton— Copernicus,  1473 
-1543— TychoBrahe,  1546-1601— Kepler,  1571-1631— Galileo,  1564 
-1642 110 

CHAPTER  XI. 

The  first  Idea  of  Gravity  occurs  to  Newton  in  1666— His  first  Specu- 
lations upon  it— Interrupted  by  his  Optical  Experiments— He 
resumes  the  Subject  in  consequence  of  a  Discussion  with  Doctor 
Hooke — He  discovers  t'je  true  Law  of  Gravity  and  the  Cause  of 
the  Planetary  Motions— Dr.  Halley  urges  him  to  publish  his  Prin- 
cipia — His  Principles  of  Natural  Philosophy — Proceedings  of  the 
Royal  Society  on  this  Subject— The  Principia  appears  in  1687— 
General  Account  of  it,  and  of  the  Discoveries  it  contains — They 
meet  with  great  Opposition,  owing  to  the  Prevalence  of  the  Carte- 
sian System — Account  of  the  Reception  and  Progress  of  the  New- 
tonian Philosophy  in  Foreign  Countries — Account  of  its  Progress 
and  Establishment  in  England 140 


CONTENTS.  15 

CHAPTER  XIL  Paga 

Doctrine  of  Infinite  Quantities— Labours  of  Pappus— Kepler—  Cava- 
leri — Roberval— Fermat — Wallis — Newton  discovers  the  Bino- 
mial Theorem  and  the  Doctrine  of  Fluxions  in  16C6 — His  Manu- 
script Work  containing  this  Doctrine  communicated  to  his  Friends 
— His  Treatise  on  Fluxions — His  Mathematical  Tracts — His  Uni- 
versal Arithmetic— His  Methodus  Differentials — His  Geornetria 
Analytica — His  Solution  of  the  Problems  proposed  by  Bernouilli 
and  Leibnitz — Account  of  the  celebrated  Dispute  respecting  the 
Invention  of  Fluxions—  Commercium  Epistolicurn — Report  of  the 
Royal  Society — General  View  of  the  Controversy 168 

CHAPTER  Xin. 

James  IT.  attacks  the  Privileges  of  the  University  of  Cambridge 
Newton  chosen  one  of  the  Dtlegates  to  resist  this  Encroachment 
—He  is  elected  a  Member  of  the  Convention  Parliament— Burning 
of  his  Manuscript — His  supposed  Derangement  of  Mind — View 
taken  of  this  by  foreign  Philosophers — His  Correspondence  with 
Mr.  Pepys  and  Mr.  Locke  at  the  time  of  his  Illness— Mr.  Milling- 
ton's  Letter  to  Mr.  Pepys  on  the  subject  of  Newton's  Illness — 
Refutation  of  the  Statement  that  he  laboured  under  Mental  De- 
rangement  200 

CHAPTER  XIV. 

No  Mark  of  National  Gratitude  conferred  upon  Newton — Friendship 
between  him  and  Charles  Montague,  afterward  Earl  of  Halifax — 
Mr. Montague  appointed  Chancellor  of  the  Exchequer  in  1604 — 
He  resolves  upon  a  Recoinage — Nominates  Mr.  Newton  Warden 
of  the  Mint  in  1695 — Mr.  Newton  appointed  Master  of  the  Mint  in 
1699— Notice  of  the  Earl  of  Halifax— Mr.  Newton  elected  Asso- 
ciate of  the  Academy  of  Sciences  in  1699 — Member  for  Cambridge 
in  1701— and  President  cf  the  Royal  Society  in  1703— Queen  Anne 
confers  upon  him  the  Honour  of  Knighthood  in  1705 — Second 
Edition  of  the  Principia,  edited  by  Cotes— His  Conduct  respectvjg 
Mr.  Ditton's  Method  of  finding  the  Longitude 223 

CHAPTER  XV. 

Respect  in  which  Newton  was  held  at  the  Court  of  George  I. — The 
Princess  of  Wales  delighted  with  his  Conversation — Leibnitz  en- 
deavours to  prejudice  the  Princess  against  Sir  Isaac  and  Locke —  ' 
Controversy  occasioned  by  his  Conduct — The  Princess  obtains  a 
Manuscript  Abstract  of  his  System  of  Chronology — The  Abbe 
Conti  is,  at  her  request,  allowed  to  take  a  Copy  of  it  on  the  prom- 
ise of  Secrecy — He  prints  it  surreptitiously  in  French,  accompa- 
nied with  a  Refutation  by  M.  Freret— Sir  Isaac's  Defence  of  his 
System— Father  Souciet  attacks  it,  and  is  answered  by  Dr.  Halley 
— Sir  Isaac's  larger  Work  on  Chronology  published  afler  his 
Death—Opinions  respecting  it— Sir  Isaac's  Paper  on  the  Form  of 
the  most  ancient  Year ••••  234 

CHAPTER  XVI. 

Theological  Studies  of  Sir  Isaac— Their  Importance  to  Christianity 
—-Motives  to  which  they  have  been  ascribed— Opinions  of  Biot 


16  CONTENTS. 

Faff 

and  La  Place  considered— His  Theological  Researches  begun  be- 
fore his  supposed  Mental  Illness— The  Date  of  these  Works  fixed 
—Letters  to  Locke— Account  of  his  Observations  on  Prophecy — 
His  Lexicon  Propheticum— His  Four  Letters  to  Dr.  Bentley— Ori 
gin  of  Newton's  Theological  Studies— Analogy  between  the  Book 
of  Nature  and  that  of  Revelation 242 

CHAPTER  XVH. 

The  Minor  Discoveries  and  Inventions  of  Newton— His  Researches 
on  Heat— On  Fire  and  Flame— On  Elective  Attraction— On  the 
Structure  of  Bodies — His  supposed  Attachment  to  Alchymy — His 
Hypothesis  respecting  Ether  as  the  Cause  of  Light  and  Gravity 
—On  the  Excitation  of  Electricity  in  Glass— His  Reflecting  Sex- 
tant invented  before  1700— His  Reflecting  Microscope— His  Pris- 
matic Reflector  as  a  Substitute  for  the  small  Speculum  of  Reflect- 
ing Telescopes— His  Method  of  varying  the  Magnifying  Power  of 
Newtonian  Telescopes— His  Experiments  on  Impressions  on  the 
Retina 265 

CHAPTER  XVIII. 

His  Acquaintance  with  Dr.  Pemberton— Who  edits  the  Third  Edi- 
tion of  the  Principia— His  first  Attack  of  ill  Health— His  Recovery 
—He  is  taken  ill  in  consequence  of  attending  the  Royal  Society — 
His  Death  on  the  20th  March,  1727— His  Body  lies  in  state— His 
Funeral— He  is  buried  in  Westminster  Abbey— His  Monument  de- 
scribed—His  Epitaph— A  Medal  struck  in  honour  of  him— Roubil- 
iac's  full-length  Statue  of  him  erected  in  Cambridge — Division 
of  his  Property— His  Successors 284 

CHAPTER  XIX. 

Permanence  of  Newton's  Reputation — Character  of  his  Genius— 
His  Method  of  Investigation  similar  to  that  used  by  Galileo — 
Error  in  ascribing  his  Discoveries  to  the  Use  of  the  Methods 
recommended  by  Lord  Bacon— The  Pretensions  of  the  Baconian 
Philosophy  examined — Sir  Isaac  Newton's  Social  Character — His 
great  Modesty— The  Simplicity  of  his  Character— His  Religious 
and  Moral  Character — His  Hospitality  and  Mode  of  Life — His 
Generosity  and  Charity— His  Absence— His  Personal  Appear- 
ance—Statues and  Pictures  of  him— Memorials  and  Recollections 
of  him 292 


APPENDIX,  No.  I.— Observations  on  the  Family  of  Sir  Isaac  New- 
ton   307 

APPENDIX,  No.  n.— Letter  from  Sir  Isaac  Newton  to  Francis  Aston, 
Esq.,  a  young  Friend  who  was  on  the  eve  of  setting  out  on  his 
Travels 318 

APPENDIX,  No.  HI.— "  A  Remarkable  and  Curious  Conversation  be- 
tween Sir  Isaac  Newton  and  Mr.  Conduit." 320 


LIFE 

off 
SIR   ISAAC    NEWTON. 


CHAPTER  I. 

The  Pre-eminence  of  Sir  Isaac  Newton's  Reputation— The  Interest 
attached  to  the  Study  of  his  Life  and  Writings— His  Birth  and 
Parentage — His  early  Education— Is  sent  to  Grantham  School — His 
early  Attachment  to  Mechanical  Pursuits— His  Windmill—His 
Waterclock — His  Selfmoving  Cart — His  Sundials — His  Preparation 
for  the  University. 

THE  name  of  Sir  Isaac  Newton  has  by  general 
consent  been  placed  at  the  head  of  those  great  men 
who  have  been  the  ornaments  of  their  species. 
However  imposing  be  the  attributes  with  which 
time  has  invested  the  sages  and  the  heroes  of  anti- 
quity, the  brightness  of  their  fame  has  been  eclipsed, 
by  the  splendour  of  his  reputation ;  and  neither  the 
partiality  of  rival  nations,  nor  the  vanity  of  a  presump- 
tuous age,  has  ventured  to  dispute  the  ascendency 
of  his  genius.  The  philosopher,*  indeed,  to  whom 
posterity  will  probably  assign  the  place  next  to  New- 
ton, has  characterized  the  Principia  as  pre-eminent 
above  all  the  productions  of  human  intellect,  and 
has  thus  divested  of  extravagance  the  contemporary 
encomium  upon  its  author, 

Nee  fas  est  propius  mortal!  attingere  Divos. 

HALLET. 
So  near  the  gods— man  cannot  nearer  go. 

I  — — — .  — 

*  The  Marquis  La  Place.— See  Systtme  du  Monde,  p.  336. 
B2 


18  SIR   ISAAC   NEWTON 

The  biography  of  an  individual  so  highly  renowned 
cannot  fail  to  excite  a  general  interest.  Though 
his  course  may  have  lain  in  the  vale  of  private  life, 
and  may  have  been  unmarked  with  those  dramatic 
events  which  throw  a  lustre  even  round  perishable 
names,  yet  the  inquiring  spirit  will  explore  the  his- 
tory of  a  mind  so  richly  endowed, — will  study  its 
intellectual  and  moral  phases,  and  will  seek  the 
shelter  of  its  authority  on  those  great  questions 
which  reason  has  abandoned  to  faith  and  hope. 

If  the  conduct  and  opinions  of  men  of  ordinary 
talent  are  recorded  for  our  instruction,  how  inter- 
esting must  it  be  to  follow  the  most  exalted  genius 
through  the  incidents  of  common  life ; — to  mark  the 
steps  by  which  he  attained  his  lofty  pre-eminence ; 
to  see  how  he  performs  the  functions  of  the  social 
and  the  domestic  compact;  how  he  exercises  his 
lofty  powers  of  invention  and  discovery;  how  he 
comports  himself  in  the  arena  of  intellectual  strife ; 
and  in  what  sentiments,  and  with  what  aspirations 
he  quits  the  world  which  he  has  adorned. 

In  almost  all  these  bearings,  the  life  and  writings 
of  Sir  Isaac  Newton  abound  with  the  richest  counsel. 
Here  the  philosopher  will  learn  the  art  by  which 
alone  he  can  acquire  an  immortal  name.  The  mor- 
alist will  trace  the  lineaments  of  a  character  ad- 
justed to  all  the  symmetry  of  which  our  imperfect 
nature  is  susceptible;  and  the  Christian  will  con- 
template with  delight  the  high-priest  of  science 
quitting  the  study  of  the  material  universe, — the 
scene  of  his  intellectual  triumphs, — to  investigate 
with  humility  and  patience  the  mysteries  of  his  faith. 

Sir  Isaac  Newton  was  born  at  Woolsthorpe,  a 
hamlet  in  the  parish  of  Colsterworth,  in  Lincoln- 
shire, about  six  miles  south  of  Grantham,  on  the 
25th  December,  O.  S.,  1642,  exactly  one  year  after 
Galileo  died,  and  was  baptized  at  Colsterworth  on 
the  1st  January,  1643-3.  His  father,  Mr.  Isaac  New- 


BIRTH.  19 

ton,  died  at  the  early  age  of  thirty-six,  a  little  more 
than  a  year  after  the  death  of  his  father  Robert 
Newton,  and  only  a  few  months  after  his  marriage 
to  Harriet  Ayscough,  daughter  of  James  Ayscough 
of  Market  Overton  in  Rutlandshire.  This  lady  was 
accordingly  left  in  a  state  of  pregnancy,  and  appears 
to  have  given  a  premature  birth  to  her  only  and 
posthumous  child.  The  helpless  infant  thus  ushered 
into  the  world  WPS  of  such  an  extremely  diminutive 
size,*  and  seemed  of  so  perishable  a  frame,  that 
two  women  who  were  sent  to  Lady  Pakenham's  at 
North  Witham,  to  bring  some  medicine  to  strengthen 
him,  did  not  expect  to  find  him  alive  on  their  return. 
Providence,  however,  had  otherwise  decreed;  and 
that  frail  tenement  which  seemed  scarcely  able  to 
imprison  its  immortal  mind  was  destined  to  enjoy 
a  vigorous  maturity,  and  to  survive  even  the  average 
term  of  human  existence.  The  estate  of  Wools- 
thorpe,  in  the  manor-house  of  which  this  remarka- 
ble birth  took  place,  had  been  more  than  a  hundred 
years  in  the  possession  of  the  family,  who  came 
originally  from  Newton  in  Lancashire,  but  who  had, 
previous  to  the  purchase  of  Woolsthorpe,  settled  at 
Westby,  in  the  county  of  Lincoln.  The  manor- 
house,  of  which  we  have  given  an  engraving,  is 
situated  in  a  beautiful  little  valley,  remarkable  for 
its  copious  wells  of  pure  spring  water,  on  the  west 
side  of  the  river  Witham,  which  has  its  origin  in  the 
neighbourhood,  and  commands  an  agreeable  pros- 
pect to  the  east  towards  Colsterworth.  The  manor 
of  Woolsthorpe  was  worth  only  30Z.  per  annum; 
but  Mrs.  Newton  possessed  another  small  estate  at 
Sewstern,f  which  raised  the  annual  value  of  their 
property  to  about  80Z. ;  and  it  is  probable  that  the 
cultivation  of  the  little  farm  on  which  she  resided 

*  Sir  Isaac  Newton  told  Mr.  Conduit,  that  he  had  often  heard  his 
mother  say  that  when  he  was  born  he  was  so  little  that  they  might 
have  put  him  into  a  quart  mug. 

t  In  Leicestershire,  and  about  three  miles  south-east  of  Woolsthorpe. 


20  SIR  ISAAC   NEWTON. 

somewhat  enlarged  the  limited  income  upon  which 
she  had  to  support  herself,  and  educate  her  child. 

For  three  years  Mrs.  Newton  continued  to  watch 
over  her  tender  charge  with  parental  anxiety ;  but 
in  consequence  of  her  marriage  to  the  Reverend 
Barnabas  Smith,  rector  of  North  Witham,  about  a 
mile  south  of  Woolsthorpe,  she  left  him  under  the 
care  of  her  own  mother.  At  the  usual  age  he  was 
sent  to  two  day-schools  at  Skillington  and  Stoke, 
where  he  acquired  the  education  which  such  semi- 
naries afforded;  but  when  he  reached  his  twelfth 
year  he  went  to  the  public  school  at  Grantham, 
taught  by  Mr.  Stokes,  and  was  boarded  at  the  house 
of  Mr.  Clark,  an  apothecary  in  that  town.  Accord- 
ing to  information  which  Sir  Isaac  himself  gave  to 
Mr.  Conduit,  he  seems  to  have  been  very  inattentive 
to  his  studies,  and  very  low  in  the  school.  The 
boy,  however,  who  was  above  him,  having  one  day 
given  him  a  severe  kick  upon  his  stomach,  from 
which  he  suffered  great  pain,  Isaac  laboured  inces- 
santly till  he  got  above  him  in  the  school,  and  from 
that  time  he  continued  to  rise  till  he  was  the  head 
boy.  From  the  habits  of  application  which  this 
incident  had  led  him  to  form,  the  peculiar  character 
of  his  mind  was  speedily  displayed.  During  the 
hours  of  play,  when  the  other  boys  were  occupied 
with  their  amusements,  his  mind  was  engrossed  with 
mechanical  contrivances,  either  in  imitation  of  some- 
thing which  he  •  had  seen,  or  in  execution  of  some 
original  conception  of  his  own.  For  this  purpose 
he  provided  himself  with  little  saws,  hatchets,  ham- 
mers, and  all  sorts  .of  tools,  which  he  acquired  the 
art -of  using  with  singular  dexterity.  The  principal 
pieces  of  mechanism  which  he  thus  constructed 
were  a  windmill,  a  waterclock,  and  a  carriage  put  in 
motion  by  the  person  who  sat  in  it.  When  a  wind- 
mill was  erecting  near  Grantham  on  the  road  to 
Gunnerby,  Isaac  frequently  attended  the  operations 
of  the  workmen,  and  acquired  such  a  thorough 


MECHANICAL  PURSUITS.  21 

knowledge  of  the  machinery  that  he  completed  a 
working  model  of  it,  which  excited  universal  admi- 
ration. This  model  was  frequently  placed  on  the  top 
of  the  house  in  which  he  lodged  at  Grantham,  and 
was  put  in  motion  by  the  action  of  the  wind  upon 
its  sails.  Not  content  with  this  exact  •  imitation  of 
the  original  machine,  he  conceived  the  idea  of  driv- 
ing it  by  animal  power,  and  for  this  purpose  he  en- 
closed in  it  a  mouse  which  he  called  the  miller,  and 
which,  by  acting  upon  a  sort  of  treadwheel,  gave 
motion  to  the  machine.  According  to  some  ac- 
counts, the  mouse  was  made  to  advance  by  pulling 
a  string  attached  to  its  tail,  while  others  allege  that 
the  power  of  the  little  agent  was  called  forth  by  its 
unavailing  attempts  to  reach  a  portion  of  corn  placed 
above  the  wheel. 

His  waterclock  was  formed  out  of  a  box  which 
he  had  solicited  from  Mrs.  Clark's  brother.  It  was 
about  four  feet  high,  and  of  a  proportional  breadth, 
somewhat  like  a  common  houseclock.  The  index 
of  the  dialplate  was  turned  by  a  piece  of  wood,  which 
either  fell  or  rose  by  the  action  of  dropping  water. 
As  it  stood  in  his  own  bedroom  he  supplied  it  every 
morning  with  the  requisite  quantity  of  water,  and  it 
was  used  as  a  clock  by  Mr.  Clark's  family,  and  re- 
mained in  the  house  long  after  its  inventor  had 
quitted  Grantham.*  His  mechanical  carriage  was  a 
vehicle  with  four  wheels,  which  was  put  in  motion 
with  a  handle  wrought  by  the  person  who  sat  in  it, 
but,  like  Merlin's  chair,  it  seems  to  have  been  used 
only  on  the  smooth  surface  of  a  floor,  and  not  fitted 
to  overcome  the  inequalities  of  a  road.  Although 

<• 

*  "I  remember  once,"  says  Dr.  Stukely,  "when  I  was  deputy  to 
Dr.  Halley,  secretary  at  the  Royal  Society,  Sir  Isaac  talked  of  these 
kind  of  instruments.  That  he  observed  the  chief  inconvenience  in 
them  was,  that  the  hole  through  which  the  water  is  transmitted  being 
necessarily  very  small,  was  subject  to  be  furred  up  by  impurities  in  the 
water,  as  those  made  with  sand  will  wear  bigger,  which  at  length  causes 
an  inequality  in  time." — Stukely 's  Letter  to  Dr.  Mead. — Tumor's  CoZ- 
lections,  p.  177. 


22  SIR   ISAAC  NEWTON. 


Newton  was  at  this  time  "  a  sober,  silent,  thinking 
lad,"  who  scarcely  ever  joined  in  the  ordinary  games 
of  his  schoolfellows,  yet  he  took  great  pleasure  in 
providing  them  with  amusements  of  a  scientific 
character.  He  introduced  into  the  school  the  flying 
of  paper  kites  ;  and  he  is  said  to  have  been  at  great 
pains  in  determining  their  best  forms  and  propor- 
tions, and  in  ascertaining  the  position  and  number 
of  the  points  by  which  the  string  should  be  attached. 
He  made  also  paper  lanterns,  by  the  light  of  which 
he  went  to  school  in  the  winter  mornings,  and  he 
frequently  attached  these  lanterns  to  the  tails  of 
his  kites  in  a  dark  night,  so  as  to  inspire  the  country 
people  with  the  belief  that  they  were  comets. 

In  the  house  where  he  lodged  there  were  some 
female  inmates  in  whose  company  he  appears  to  have 
taken  much  pleasure.  One  of  these,  a  Miss  Storey, 
sister  to  Dr.  Storey,  a  physician  at  Buckminster, 
near  Colsterworth,  was  two  or  three  years  younger 
than  Newton,  and  to  great  personal  attractions  she 
seems  to  have  added  more  than  the  usual  allotment 
of  female  talent.  The  society  of  this  young  lady 
and  her  companions  was  always  preferred  to  that 
of  his  own  schoolfellows,  and  it  was  one  of  his  most 
agreeable  occupations  to  construct  for  them  little 
tables  and  cupboards,  and  other  utensils  for  holding 
their  dolls  and  their  trinkets.  He  had  lived  nearly 
six  years  in  the  same  house  with  Miss  Storey,  and 
there  is  reason  to  believe  that  their  youthful  friend- 
ship gradually  rose  to  a  higher  passion;  but  the 
smallness  of  her  portion  and  the  inadequacy  of  his 
own  fortune  appear  to  have  prevented  the  consum- 
mation of  their  happiness.  Miss  Storey  was  after- 
ward twice  married,  and  under  the  name  of  Mrs. 
Vincent,  Dr.  Stukely  visited  her  at  Grantham  in  1727, 
at  the  age  of  eighty-two,  and  obtained  from  her 
many  particulars  respecting  the  early  history  of  our 
author.  Newton's  esteem  for  her  continued  un- 
abated during  his  life.  He  regularly  visited  her  when 


SUNDIALS.  23 

he  went  to  Lincolnshire,  and  never  failed  to  relieve 
her  from  little  pecuniary  difficulties  which  seem  to 
have  beset  her  family. 

Among  the  early  passions  of  Newton  we  must 
recount  his  love  of  drawing ;  and  even  of  writing 
verses.  His  own  room  was  furnished  with  pictures 
drawn,  coloured,  and  framed  by  himself,  sometimes 
from  copies,  but  often  from  life.*  Among  these 
were  portraits  of  Dr.  Donne,  Mr.  Stokes,  the  master 
of  Grantham  school,  and  King  Charles  I.  under 
whose  picture  were  the  following  verses. 

A  secret  art  my  soul  requires  to  try, 
If  prayers  can  give  me  what  the  wars  deny. 
Three  crowns  distinguished  here,  in  order  do 
Present  their  objects  to  my  knowing  view. 
Earth's  crown,  thus  at  my  feet  I  can  disdain, 
Which  heavy  is,  and  at  the  best  but  vain. 
But  now  a  crown  of  thorns  I  gladly  greet, 
Sharp  is  this  crown,  but  not  so  sharp  as  sweety 
The  crown  of  glory  that  I  yonder  see 
Is  full  of  bliss  and  of  eternity. 

These  verses  were  repeated  to  Dr.  Stukely  by  Mrs. 
Vincent,  who  believed  them  to  be  written  by  Sir 
Isaac,  a  circumstance  which  is  the  more  probable, 
as  he  himself  assured  Mr.  Conduit,  with  some  ex- 
pression of  pleasure,  tHat  he  "  excelled  in  making 
verses,"  although  he  had  been  heard  to  express  a 
contempt  for  poetical  composition. 

But  while  the  mind  of  our  young  philosopher  was 
principally  occupied  with  the  pursuits  which  we  have 
now  detailed,  it  was  not  inattentive  to  the  move- 
ments of  the  celestial  bodies,  on  which  he  was  des- 
tined to  throw  such  a  brilliant  light.  The  imperfec- 
tions of  his  watei  clock  had  probably  directed  his 
thoughts  to  the  more  accurate  measure  of  time  which 
the  motion  of  the  sun  afforded.  In  the  yard  of  the 

*  Mr.  Clark  informed  Dr.  Stukely  that  the  walls  of  the  room  in  which 
Sir  Isaac  lodged  were  covered  with  charcoal  drawings  of  birds,  beasts, 
men,  ships,  and  mathematical  figures,  ail  of  which  were  very  well  de- 
signed. 


24  SIR  ISAAC   NEWTON. 

house  where  he  lived,  he  traced  the  varying  move- 
ments of  that  luminary  upon  the  walls  and  roofs  of  the 
buildings,  and  by  means  of  fixed  pins  he  had  marked 
out  the  hourly  and  half-hourly  subdivisions.  One 
of  these  dials,  which  went  by  the  name  of  Isaac's 
<foz/,and  was  often  referred  to  by  the  country  people 
for  the  hour  of  the  day,  appears  to  have  been  drawn 
solely  from  t"Lo  observations  of  several  years ;  but 
we  are  not  informed  whether  all  the  dials  *which  he 
drew  on  the  wall  of  his  house  at  Woolsthorpe,  and 
which  existed  after  his  death,  were  of  the  same 
description,  or  were  projected  from  his  knowledge 
of  the  doctrine  of  the  sphere. 
>  Upon  the  death  of  the  Reverend  Mr.  Smith  in  the 
year  1656,  his  widow  left  the  rectory  of  North 
Witham,  and  took  up  her  residence  at  Woolsthorpe 
along  with  her  three  children,  Mary,  Benjamin,  and 
Hannah*  Smith.  Newton  had  now  attained  the 
fifteenth  year  of  his  age,  and  had  made  great  pro- 
gress in  his  studies ;  and  as  he  was  thought  capable 
of  being  useful  in  the  management  of  the  farm  and 
country  business  at  Woolsthorpe,  his  mother,  chiefly 
from  a  motive  of  economy,  recalled  him  from  the 
school  at  Grantham.  In  order  to  accustom  him  to 
the  art  of  selling  and  buying,  two  of  the  most  im- 
portant branches  of  rural  labour,  he  was  frequently 
sent  on  Saturday  to  Grantham  market  to  dispose 
of  grain  and  other  articles  of  farm  produce,  and  to 
purchase  such  necessaries  as  the  family  required. 
As  he  had  yet  acquired  no  experience,  an  old  trust- 
worthy servant  generally  accompanied  him  on  these 
errands.  The  inn  which  they  patronised  was  the 
Saracen's  Head  at  West  Gate ;  but  no  sooner  had 
they  put  tip  their  horses  than  our  young  philosopher 
deserted  his  commercial  concerns,  and  betook  him- 
self to  his  former  lodging  in  the  apothecary's  garret, 
where  a  number  of  Mr.  Clark's  old  books  afforded 
him  abundance  of  entertainment  till  his  aged  guar- 
dian had  executed  the  family  commissions,  and  a& 


PREPARATION   FOR   THE    UNIVERSITY.  2 

nounced  to  him  the  necessity  of  returning.  At  other 
times  he  deserted  his  duties  at  an  earlier  stage,  and 
intrenched  himself  under  a  hedge  by  the  way-side, 
where  he  continued  his  studies  till  the  servant  re- 
turned from  Grantham.  The  more  immediate  affairs 
of  the  farm  were  not  more  prosperous  under  his 
management  than  would  have  been  his  marketings 
at  Grantham.  The  perusal  of  a  book,  the  execu- 
tion of  a  model,  or  the  superintendence  of  a  water- 
wheel  of  his  own  construction,  whirling  the  glitter- 
ing spray  from  some  neighbouring  stream,  absorbed 
all  his  thoughts  when  the  sheep  were  going  astray, 
and  the  cattle  were  devouring  or  treading  down  the 
corn. 

Mrs.  Smith  was  soon  convinced  from  experience 
that  her  son  was  not  destined  to  cultivate  the  soil, 
and  as  his  passion  for  study,  and  his  dislike  for  every 
other  occupation  increased  with  his  years,  s?ie  wisely 
resolved  to  give  him  all  the  advantages  which  edu- 
cation could  confer^  He  was  accordingly  sent  back 
to  Grantham  school,  where  he  continued  for  some 
months  in  busy  preparation  for  his  academical  stu- 
dies. His  uncle,  the  Reverend  W.  Ayscough,  who 
was  rector  of  Burton  Goggles,  about  three  miles 
east  of  Woolsthorpe,  and  who  had  himself  studied 
at  Trinity  College,  recommended  to  his  nephew  to 
enter  that  society,  and  it  was  accordingly  determined 
that  he  should  proceed  to  Cambridge  at  the  ap- 
proaching term.* 

*  "  One  of  his  uncles,"  says  M.  Biot,  "  having  one  day  found  him 
under  a  hedge  with  a  book  in  his  hand  and  entirely  absorbed  in  medita- 
tion, took  it  from  him,  and  found  that  he  was  occupied  in  the  solution  of  a 
mathematical  problem.  Struck  with  finding  so  serious  and  so  active 
a  disposition  at  so  early  an  age,  he  urged  his  mother  no  longer  to  thwart 
iHm,  and  to  send  him  back  to  Grantham  to  continue  his  studies."  I 
hsve  omitted  this  anecdote  in  the  text,  as  I  cannot  find  it  in  Tumor's 
Collections,  from  which  M.  Biot  derived  his  details  of  Newton's  infancy, 
Ifc»r  in  any  other  work. 

c 


26  SIR  ISAAC   NEWf ON. 


CHAPTER  II. 

fffwton  enters  Trinity  College,  Cambridge—Origin  of  his  Propensity 
for  Mathematics— He  studies  the  Geometry  ofDetcartes  unassisted—- 
Purchases a  Prism — Revises  Dr.  Harrow's  Optical  Lectures — Dr 
Barrow's  Opinion  respecting  Colours.— Takes  his  Degrees — Is  ap- 
pointed a  Fellow  of  Trinity  College —Succeeds  Dr.  Barrow  in  the 
Lucasian  Chair  of  Mathematics. 

To  a  young  mind  thirsting  for  knowledge,  and 
ambitious  of  the  distinction  which  it  brings,  the 
transitibn  from  a  village  school  to  a  university  like 
that  of  Cambridge, — from  the  absolute  solitude  of 
thought  to  the  society  of  men  imbued  with  all  the 
literature  and  science  of  the  age, — must  be  one  of 
eventful  interest.  To  Newton  it  was  a  source  of 
peculiar  excitement.  The  history  of  science  affords 
many  examples  where  the  young  aspirant  had  been 
early  initiated  into  her  mysteries,  and  had  even  ex- 
ercised his  powers  of  invention  and  discovery  before 
he  was  admitted  within  the  walls  of  a  college ;  but  he 
who  was  to  give  philosophy  her  laws  did  not  exhibit 
such  early  talent ;  no  friendly  counsel  regulated  his 
youthful  studies,  and  no  work  of  scientific  eminence 
seems  to  have  guided  him  in  his  course.  In  yield- 
ing to  the  impulse  of  his  mechanical  genius,  his 
mind  obeyed  the  laws  of  its  own  natural  expansion, 
and,  following  the  line  of  least  resistance,  it  was 
thus  drawn  aside  from  the  strongholds  with  which 
it  was  destined  to  grapple. 

When  Newton,  therefore,  arrived  at  Trinity  Col- 
lege, he  brought  with  him  a  more  slender  portion  of 
science  than  falls  to  the  lot  of  ordinary  scholars ; 
but  this  state  of  his  acquirements  was  perhaps  not 
unfavourable  to  the  development  of  his  powers. 
Unexhausted  by  premature  growth,  and  invigorated 
by  healthful  repose,  his  mind  was  the  better  fitted  to 


TRINITY    COLLEGE.  27 

make  those  vigorous  and  rapid  shoots  which  soon 
covered  with  foliage  and  with  fruit  the  genial  soil 
to  which  it  had  been  transferred. 
^•Cambridge  was  consequently  the  real  birthplace 
of  Newton's  genius.  Her  teachers  fostered  his  ear- 
liest studies ; — her  institutions  sustained  his  mightiest 
efforts ; — and  within  her  precincts  were  all  his  dis- 
coveries made  and  perfected.  When  he  was  called 
to  higher  official  functions,  his  disciples  kept  up  the 
pre-eminence  of  their  master's  philosophy,  and  their 
successors  have  maintained  this  seat  of  learning  in, 
the  fulness  of  its  glory,  and  rendered  it  the  most 
distinguished  among  the  universities  of  Europe. 

It  was  on  the  5th  of  June,  1660,  in  the  18th  year 
of  his  age,  that  Newton  was  admitted  into  Trinity 
College,  Cambridge,  during  the  same  year  that  Dr. 
Barrow  was  elected  professor  of  Greek  in  the  uni- 
versity. His  attention  was  first  turned  to  the  study 
of  mathematics  by  a  desire  to  inquire  into  the  truth 
of  judicial  astrology ;  and  he  is  said  to  have  dis- 
covered the  folly  of  that  study  by  erecting  a  figure 
with  the  aid  of  one  or  two  of  the  problems  of 
Euclid.  The  propositions  contained  in  this  ancient 
system  of  geometry  he  regarded  as  self-evident 
truths ;  and  without  any  preliminary  study  he  made 
himself  master  of  Descartes's  Geometry  by  his 
genius  and  patient  application.  This  neglect  of  the 
elementary  truths  of  geometry  he  afterward  regarded 
as  a  mistake  in  his  mathematical  studies,  and  he  ex- 
pressed to  Dr.  Pemberton  his  regret  that  "  he  had  ap- 
plied himself  to  the  works  of  Descartes,  and  other  alge- 
oraic  writers,  before  he  had  considered  the  elements 
of  Euclid  with  that  attention  which  so  excellent  a 
writer  deserved.*  Dr.  Wallis's  Arithmetic  of  Infinites, 
^aunderson's  Logic,  and  the  Optics  of  Kepler  were 
among  the  books  which  he  had  studied  with  care.  On 
these  works  he  wrote  comments  during  their  perusal  $ 

*  Pemberton's  View  of  Sir  Isaac  Newton1  s  Philosophy.    Pref.        _, 


28  SIR  ISAAC   NEWTON. 

and  so  great  was  his  progress,  that  he  is  reported  to 
have  found  himself  more  deeply  versed  in  some 
branches  of  knowledge  than  the  tutor  who  directed 
his  studies. 

Neither  history  nor  tradition  has  handed  down  to 
us  any  particular  account  of  his  progress  during  the 
first  three  years  that  he  spent  at  Cambridge.  It 
appears  from  a  statement  of  his  expenses,  that  in 
1664  he  purchased  a  prism,  for  the  purpose,  as  has 
been  said,  of  examining  rtescartes's  theory  of  co- 
lours ;  and  it  is  stated  by  Mr.  Conduit,  that  he  soon 
established  his  own  views  on  the  subject,  and  de- 
tected the  errors  in  those  of  the  French  philosopher. 
This,  however,  does  not  seem  to  have  been  the  case. 
Had  he  discovered  the  composition  of  light  in  1664 
or  1665,  it  is  not  likely  that  he  would  have  withheld 
it,  not  only  from  the  Royal  Society,  but  from  his 
own  friends  at  Cambridge  till  the  year  1671.  His 
friend  and  tutor,  Dr.  Barrow,  was  made  Lucasian 
Professor  of  Mathematics  in  1663,  and  the  optical 
lectures  which  he  afterward  delivered  were  published 
in  1669.  In  the  preface  of  this  work  he  acknow- 
ledges his  obligations  to  his  colleague,  Mr.  Isaac 
Newton,*  for  having  revised  the  MSS.,  and  corrected 
several  oversights,  and  made  some  important  sug- 
gestions. In  the  twelfth  lecture  there  are  some  ob- 
servations on  the  nature  and  origin  of  colours, 
which  Newton  could  not  have  permitted  his  friend 
to  publish  had  he  been  then  in  possession  of  their 
true  theory.  According  to  Dr.  Barrow,  White  is 
that  which  discharges  a  copious  light  equally  clear 
in  eveiy  direction;  Black  is  that  which  does  not 
emit  light  at  all,  or  which  does  it  very  sparingly. 
Red  is  that  which  emits  a  light  more  clear  than 
usual,  but  interrupted  by  shady  interstices.  Blue  is 
that  which  discharges  a  rarified  light,  as  in  bodies 
which  consist  of  white  and  black  particles  arranged 

*  Peregregiae  vir  indolls  ac  insignia  peritiee.— Epist  ad.  Lect 


APPOINTED   PROFESSOR  ~OF   MATHEMATICS.      29 

alternately.  Green  is  nearly  allied  to  blue.  Yellow 
is  a  mixture  of  much  white  and  a  little  red;  and 
Purple  consists  of  a  great  deal  of  blue  mixed  with 
a  small  portion  of  red. .  The  blue  colour  of  the  sea 
arises  from  the  whiteness  of  the  salt  which  it  con- 
tains, mixed  with  tjie  blackness  of  the  pure  water 
in  which  the  salt  is  dissolved ;  and  the  blueness  of 
the  shadows  of  bodies,  seen  at  the  same  time  by 
candle  and  daylight,  arises  from  the  whiteness  of 
the  paper  mixed  with  the  faint  light  or  blackness  of 
the  twilight.  These  opinions  savour  so  little  of 
genuine  philosophy  that  they  must  have  attracted 
the  observation  of  Newton,  and  had  he  discovered 
at  that  time  that  white  was  a  mixture  of  all  the 
colours,  and  black  a  privation  of  them  all,  he  could 
not  have  permitted  the  absurd  speculations  of  his 
!  master  to  pass  uncorrected. 

That  Newton  had  not  distinguished  himself  by 
!  any  positive  discovery  so  early  as  1664  or  1665,  may 
!  be  inferred  also  from  the  circumstances  which  at- 
!  tended  the  competition  for  the  law  fellowship  of 
j  Trinity  College.  The  candidates  for  this  appoint- 
|  ment  were  himself  and  Mr.  Robert  Uvedale ;  and 
j  Dr.  Barrow,  then  Master  of  Trinity,  having  found 
j  them  perfectly  equal  in  their  attainments,  con- 
!  ferred  the  fellowship  on  Mr.  Uvedale  as  the  senior 
I  candidate. 

In  the  books  of  the  university,  Newton  is  recorded 
j  as  having  been  admitted  sub-sizer  in  1661.      He 
!  became  a  scholar  in  1664.     In  1665  he  took  his  de- 
gree of  Bachelor  of  Arts,  and  in  1666,  in  conse- 
quence of  the  breaking  out  of  the  plague,  he  retired 
to  Woolsthorpe.     In  1667  he  was  made  Junior  Fel- 
low.   In  1668  he  took  his  degree  of  Master  of  Arts, 
and  in  the  same  year  he  was  appointed  to  a  Senior 
Fellowship.      In  1669,  when  Dr.  Barrow  had  re- 
solved to  devote  his  attention  to  theology,  he  re- 
signed the  Lucasian  Professorship  of  Mathematics 
in  favour  of  Newton,  who  may  now  be  considered 
C2 


30  SIR   ISAAC   NEWTON. 

as  having  entered  upon  that  brilliant  career  of  dis- 
covery the  history  of  which  will  form  the  subject  of 
some  of  the  following  chapters. 


CHAPTER  III. 

Newton  occupied  in  grinding  Hyperbolical  Lenses— His  first  Experi- 
ments with  the  Prism  made  in  1666 — He  discovers  the  Composition  of 
White  Light,  and  the  different  Refrangibility  of  the  Rays  which  com- 
pose it— Abandons  his  Attempts  to  improve  Refracting  Telescopes  and 
resolves  to  attempt  the  Construction  of  Reflecting  ones — He  quits  Cam- 
bridge on  account  of  the  Plague — Constructs  two  Reflecting  Telescopes 
in  1668,  the  first,  ever  executed—  One  of  them  examined  by  the  Royal  So- 
ciety, and  shown  to  the  King — He  constructs  a  Telescope  with  Glass 
Specula— Recent  History  of  the  Reflecting  Telescope— Mr.  Airy's 
Glass  Specula— Hadleifs  Reflecting  Telescopes— Short's— HerscheCs 
— Ramage's — Lord  Oxmantowrts. 

THE  appointment  of  Newton  to  the  Lucasian 
chair  at  Cambridge  seems  to  have  been  coeval  with 
his  grandest  discoveries.  The  first  of  these  of 
which  the  date  is  well  authenticated  is  that  of  the 
different  refrangibility  of  the  rays  of  light,  which  he 
established  in  1666.  The  germ  of  the  doctrine  of 
universal  gravitation  seems  to  have  presented  itself 
to  him  in  the  same  year,  or  at  least  in  1667  •  and  uin 
the  year  1666  or  before"*  he  was  in  possession  of 
his  method  of  fluxions,  and  he  had  brought  it  to  such 
a  state  in  the  beginning  of  1669,  that  he  permitted 
Dr.  Barrow  to  communicate  it  to  Mr.  Collins  on  the 
20th  of  June  in  that  year. 

Although  we  have  already  mentioned,  on  the  au- 
thority of  a  written  memorandum  of  Newton  him 
self,  that  he  purchased  a  prism  at  Cambridge  in  1664, 
yet  he  does  not  appear  to  have  made  any  use  of  it, 
as  he  informs  us  that  it  was  in  1666  that  he  "pro- 

*  See  Newton's  Letter  to  the  Abbe  Conti,  dated  February  26, 1715-lft 
hi  the  Additamenta  Comm.  Epistotici. 


REFRACTING  TELESCOPE.         31 

cured  a  triangular  glass  prism  to  try  therewith  the 
celebrated  phenomena  of  colours."*  During  that 
year  he  had  applied  himself  to  the  grinding  of  "  op- 
tic glasses,  of  other  figures  than  spherical,"  and 
having,  no  doubt,  experienced  the  impracticability 
of  executing  such  lenses,  the  idea  of  examining  the 
phenomena  of  colour  was  one  of  those  sagacious 
and  fortunate  impulses  which  more  than  once  led 
him  to  discovery.  Descartes  in  his  Dioptrice,  pub- 
lished in  1629,  and  more  recently  James  Gregory  in 
his  Optica  Promota  published  in  1663,  had  shown 
that  parallel  and  diverging  rays  could  be  reflected  or 
refracted,  with  mathematical  accuracy,  to  a  point  or 
focus,  by  giving  the  surface  a  parabolic,  an  elliptical, 
or  a  hyperbolic  form,  or  some  other  form  not  spher- 
ical. Descartes  had  even  invented  and  described 
machines  by  which  lenses  of  these  shapes  could  be 
ground  and  polished,  and  the  perfection  of  the  re- 
fracting telescope  was  supposed  to  depend  on  the 
degree  of  accuracy  with  which  they  could  be  exe- 
cuted. 

In  attempting  to  grind  glasses  that  were  not  spher- 
ical, Newton  seems  to  have  conjectured  that  the  de- 
fects of  lenses,  and  consequently  of  refracting  tele- 
scopes, might  arise  from  some  other  cause  than  the 
imperfect  convergency  of  rays  to  a  single  point,  and 
this  conjecture  was  happily  realized  in  those  fine 
discoveries  of  which  we  shall  now  endeavour  to 
give  some  account. 

!  When  Newton  began  this  inquiry,  philosophers  of 
the  highest  genius  were  directing  all  the  energies  of 
their  mind  to  the  subject  of  light,  and  to  the  im- 
provement of  the  refracting  telescope.  James 
Gregory  of  Aberdeen  had  invented  his  reflecting 
telescope.  Descartes  had  explained  the  theory  and 
exerted  himself  in  perfecting  the  construction  of  the 
common  refracting  telescope,  and  Huygens  had  not 

•  Newtoni  Opera,  torn,  iv.  p.  205,  Letter  to  Oldenburg. 


32  SIR  ISAAC  NEWTON. 

only  executed  the  magnificent  instruments  by  which 
he  discovered  the  ring  and  the  satellites  of  Saturn, 
but  had  begun  those  splendid  researches  respecting 
the  nature  of  light,  and  the  phenomena  of  double 
refraction,  which  have  led  his  successors  to  such 
brilliant  discoveries.  Newton,  therefore,  arose  when 
the  science  of  light  was  ready  for  some  great  ac- 
cession, and  at  the  precise  time  when  he  was  re- 
quired to  propagate  the  impulse  which  it  had  received 
from  his  illustrious  predecessors. 

The  ignorance  which  then  prevailed  respecting 
the  nature  and  origin  of  colours  is  sufficiently  ap- 
parent from  the  account  we  have  already  given  of 
Dr.  Barrow's  speculations  on  this  subject.  It  was 
always  supposed  that  light  of  every  colour  was 
equally  refracted  or  bent  out  of  its  direction  when 
it  passed  through  any  lens  or  prism,  or  other  refract- 
ing medium ;  and  though  the  exhibition  of  colours 
by  the  prism  had  been  often  made  previous  to  the 
time  of  Newton,  yet  no  philosopher  seems  to  have 
attempted  to  analyze  the  phenomena. 

When  he  had  procured  his  triangular  glass  prism, 
a  section  of  which  is  shown  at  ABC,  (fig.  1,)  he 

Fig.  1. 


made  a  hole  H  in  one  of  his  window-shutters,  SHT 
and  having  darkened  his  chamber,  he  let  in  a  con- 
venient quantity  of  the  sun's  light  RR,  which,  pass- 


EXPERIMENTS    ON    COLOURS.  33 

ing  through  the  prism  ABC,  was  so  refracted  as  to 
exhibit  all  the  different  colours  on  the  wall  at  MN, 
forming  an  image  about  five  times  as  long  as  it  was 
broad.  "It  was  at  first,"  says  our  author,  "a  very 
pleasing  divertisement  to  view  the  vivid  and  intense 
colours  produced  thereby,"  but  this  pleasure  was 
immediately  succeeded  by  surprise  at  various  circum- 
stances which  he  had  not  expected.  According  to 
the  received  laws  of  refraction,  he  expected  the 
image  MN  to  be  circular,  like  the  white  image  at  W, 
which  the  sunbeam  RR  had  formed  on  the  wall 
previous  to  the  interposition  of  the  prism ;  but  when 
he  found  it  to  be  no  less  than  five  times  larger  than 
its  breadth,  it  "excited  in  him  a  more  than  ordinary 
curiosity  to  examine  from  whence  it  might  proceed. 
He  could  scarcely  think  that  the  various  thickness  of 
the  glass,  or  the  termination  with  shadow  or  dark- 
ness, could  have  any  influence  on  light  to  produce  such 
an  effect:  yet  he  thought  it  not  amiss  first  to  examine 
those  circumstances,  and  so  find  what  would  happen 
by  transmitting  light  through  parts  of  the  glass  of 
divers  thicknesses,  or  through  holes  in  the  window 
of  divers  bignesses,  or  by  setting  the  prism  without 
(on  the  other  side  of  ST),  so  that  the  light  might 
pass  through  it  and  be  refracted  before  it  was  termi- 
nated by  the  hole ;  but  he  found  none  of  these  cir- 
cumstances material.  The  fashion  of  the  colours 
was  in  all  those  cases  the  same." 

Newton  next  suspected  that  some  unevenness  in 
the  glass,  or  other  accidental  irregularity,  might 
cause  the  dilatation  of  the  colours.  In  order  to  try 
this,  he  took  another  prism  BCB',  and  placed  it  in 
such  a  manner  that  the  light  RRW  passing  through 
them  both  might  be  refracted  contrary  ways,  and 
thus  returned  by  BCB'  into  that  course  RRW,  from 
which  the  prism  ABC  had  diverted  it,  for  by  this 
means  he  thought  the  regular  effects  of  the  prism 
ABC  would  be  destroyed  by  the  prism  BCB,  and  the 
irregular  ones  more  augmented  by  the  multiplicity 


34  SIR   ISAAC   NEWTON. 

of  refractions.  The  result  was,  that  the  light  which 
was  diffused  by  the  first  prism  ABC  into  an  oblong 
form,  was  reduced  by  the  second  prism  BCB'  into  a 
circular  one  W,  with  as  much  regularity  as  when  it 
did  not  pass  through  them  at  all;  so  that  whatever 
was  the  cause  of  the  length  of  the  image  MN,  it  did 
not  arise  from  any  irregularity  in  the  prism. 

Our  author  next  proceeded  to  examine  more  critic- 
ally what  might  be  effected  by  the  difference  of  the 
incidence  of  "the  rays  proceeding  from  different  parts 
of  the  sun's  disk ;  but  by  taking  accurate  measures 
of  the  lines  and  angles,  he  found  that  the  angle  of 
the  emergent  rays  should  be  31  minutes  equal  to  the 
sun's  diameter,  whereas  the  real  angle  subtended  by 
MN  at  the  hole  H  was  2°  49'.  But  as  this  computa- 
tion was  founded  on  the  hypothesis,  that  the  sine  of 
the  angle  of  incidence  was  proportional  to  the  sine 
of  the  angle  of  refraction,  which  from  his  own  ex- 
perience he  could  not  imagine  to  be  so  erroneous  as 
to  make  that  angle  but  31',  which  was  in  reality  2° 
49',  yet  "  his  curiosity  caused  him  again  to  take  up 
his  prism"  ABC,  and  having  turned  it  round  in  both 
directions,  so  as  to  make  the  rays  RR  fall  both  with 
greater  and  with  less  obliquity  upon  the  face  AC,  he 
found  that  the  colours  on  the  wall  did  not  sensibly 
change  their  place ;  and  hence  he  obtained  a  decided 
proof  that  they  could  not  be  occasioned  by  a  differ- 
ence in  the  incidence  of  the  light  radiating  from  dif- 
ferent parts  of  the  sun's  disk. 

Newton  then  began  to  suspect  that  the  rays,  after 
passing  through  the  prism,  might  move  in  curve  lines, 
and,  in  proportion  to  the  different  degrees  of  curva- 
ture, might  tend  to  different  parts  of  the  wall;  and 
this  suspicion  was  strengthened  by  the  recollection 
that  he  had  often  seen  a  tennis-ball  struck  with  an 
oblique  racket  describe  such  a  curve  line.  In  this 
case  a  circular  and  a  progressive  motion  is  commu- 
nicated to  the  ball  by  the  stroke,  and  in  consequence 
of  this,  the  direction  of  its  motion  was  curvilineal, 


sot1 


EXPERIMENTS    ON   COLOURS.  35 

so  that  if  the  rays  of  light  were  globular  bodies, 
they  might  acquire  a  circulating  motion  by  their  ob- 
ilique  passage  out  of  one  medium  into  another,  and 
thus  move  like  the  tennis-ball  in  a  curve  line.  Not- 
withstanding, however,  "this  plausible  ground  of 
suspicion,"  he  could  discover  no  such  curvature  in 
their  direction,  and,  what  was  enough  for  his  pur- 

Eose,  he  observed  that  the  difference  between  the 
?ngth  MN  of  the  image,  and  the  diameter  of  the 
!hole  H,  was  proportional  to  their  distance  HM, 
which  could  not  have  happened  had  the  rays  moved 
in  curvilineal  paths. 

These  different  hypotheses,  or  suspicions,  as  New- 
jton  calls  them,  being  thus  gradually  removed,  he 
was  at  length  led  to  an  experiment  which  deter- 
mined beyond  a  doubt  the  true  cause  of  the  elonga- 
tion of  the  coloured  image.  Having  taken  a  board 
with  a  small  hole  in  it,  he  placed  it  behind  the  face 
BC  of  the  prism,  and  close  to  it,  so  that  he  could 
transmit  through  the  hole  any  one  of  the  colours  in 
MN,  and  keep  back  all  the  rest.  When  the  hole, 
for  example,  was  near  C,  no  other  light  but  the  red 
fell  upon  the  wall  at  N.  He  then  placed  behind  N 
another  board  with  a  hole  in  it,  and  behind  this 
board  he  placed  another  prism,  so  as  to  receive  the 
red  light  at  N,  which  passed  through  this  hole  in  the 
second  board.  He  then  turned  round  the  first  prism 
ABC  so  as  to  make  all  the  colours  pass  in  succession 
through  these  two  holes,  and  he  marked  their  places 
on  the  wall.  From  the  variation  of  these  places, 
he  saw  that  the  red  rays  at  N  were  less  refracted  by 
the  second  prism  than  the  orange  rays,  the  orange 
less  than  the  yellow,  and  so  on,  the  violet  being  more 
refracted  than  all  the  rest. 

Hence  he  drew  the  grand  conclusion,  that  light 
leas  not  homogeneous,  but  consisted  of  rays,  some  of 
which  were  more  refrangible  than  others. 

As  soon  as  this  important  truth  was  established, 
Sir  Isaac  saw  that  a  lens  which  refracts  light  exactly 


36  SIR    ISAAC    NEWTON. 

like  a  prism  must  also  refract  the  differently  colourec 
rays  with  different  degrees  of  force,  bringing  the 
violet  rays  to  a  focus  nearer  the  glass  than  the  rec 
rays.  This  is  shown  in  Jig.  2,  where  LL  is  a  con 
vex  lens,  and  S,  L,  SL  rays  of  the  sun  falling  upon  i 

Fig.  2. 

M 


M 


in  parallel  directions.  The  violet  rays  existing  in 
the  white  light  SL  being  more  refrangible  than  the 
rest,  will  be  more  refracted  or  bent,  and  will  meet  al 
V,  foiming  there  a  violet  image  of  the  sun.  In  like 
manner  the  yellow  rays  will  form  an  image  of  the 
sun  at  Y,  and  so  on,  the  red  rays,  which  are  the  least 
refrangible,  being  brought  to  a  focus  at  R,  and  there 
forming  a  red  image  of  the  sun. 

Hence,  if  we  suppose  LL  to  be  the  object-glass  of 
a  telescope  directed  to  the  sun,  and  MM  an  eye-glass 
through  which  the  eye  at  E  sees  magnified  the  image 
or  picture  of  the  sun  formed  by  LL,  it  cannot  see| 
distinctly  all  the  different  images  between  R  and  V. 
If  it  is  adjusted  so  as  to  see  distinctly  the  yellow 
ima^e  at  Y,  as  it  is  in  the  figure,  it  will  not  see  dis- 
tinctly either  the  red  or  violet  images,  nor  indeed  any 
of  them  but  the  yellow  one.  There  will  conse- 
quently be  a  distinct  yellow  image,  with  indistinct 
images  of  all  the  other  colours,  producing  great  cone- 
fusion  and  indistinctness  of  vision.  As  soon  as  Sir 
Isaac  perceived  this  result  of  his  discovery,  he  aban- 
doned his  attempts  to  improve  the  refracting  tele- 


IMPERFECTIONS  OF  TELESCOPES.      37 

•scope,  and  took  into  consideration  the  principle  of  re- 
jection; and  as  he  found  that  rays  of  all  colours 
were  reflected  regularl) ,  so  that  the  angle  of  reflec- 
tion was  equal  to  the  angle  of  incidence,  he  con- 
pluded  that,  upon  this  principle,  optical  instruments 
Plight  be  brought  to  any  degree  of  perfection  imaginable, 
[provided  a  reflecting  substance  could  be  found  which 
3ould  polish  as  finely  as  glass,  and  reflect  as  much 
light  as  glass  transmits,  and  provided  a  method  of 
:ommunicating  to  it  a  parabolic  figure  could  be  ob- 
tained. These  difficulties,  however,  appeared  to  him 
very  great,  and  he  even  thought  them  insuperable 
when  he  considered  that,  as  any  irregularity  in  a  re- 
lecting  surface  makes  the  rays  deviate  five  or  six 
times  more  from  their  true  path  than  similar  irregu- 
.arities  in  a  refracting  surface,  a  much  greater  de- 
gree of  nicety  would  be  required  in  figuring  reflect- 
ing specula  than  refracting  lenses. 

Such  was  the  progress  of  Newton's  optical  dis- 
coveries, when  he  was  forced  to  quit  Cambridge  in 
1666  by  the  plague  which  then  desolated  England, 
and  more  than  two  years  elapsed  before  he  pro- 
ceeded any  farther.  In  1668  he  resumed  the  inquiry, 
and  having  thought  of  a  delicate  method  of  polish- 
ng,  proper  (for  metals,  by  which,  as  he  conceived, 
'the  figure  would  be  corrected  to  the  last," he  began 
;o  put  this  method  to  the  test  of  experiment.  At 
,his  time  he  was  acquainted  with  the  proposal  of 
Mr.  James  Gregory,  contained  in  his  Optica  Promota, 
o  construct  a  reflecting  telescope  with  two  concave 
specula,  the  largest  of  which  had  a  hole  in  the 
middle  of  the  larger  speculum,  to  transmit  the  light 
o  an  eye-glass;*  but  he  conceived  that  it  would  be 

*  M.  Biot,  in  his  Life  of  Newton,  has  stated  that  Newton  was  pre- 
ceded in  the  invention  of  the  reflecting  telescope  by  Gregory,  but  proba- 
Ay  without  knowing  it.  It  is  quite  certain,  however,  that  Newton  was 
icquainted  with  Gregory's  invention,  as  appears  from  the  following 
avowal  of  it.  "  When  I  first  applied  myself  to  try  the  effects  of  reflec- 
tion, Mr.  Gregory's  Optica  Promota  (printed  in  the  year  1663)  having 
fallen  into  my  hands,  where  there  is  an  instrument  described  with  a  hole 


38  SIR   ISAAC   NEWTON. 

an  improvement  on  this  instrument  to  place  the  eye* 
glass  at  the  side  of  the  tube,  and  to  reflect  the  rays 
to  it  by  an  oval  plane  speculum.  One  of  these 
instruments  he  actually  executed  with  his  own 
hands ;  and  he  gave  an  account  of  it  in  a  letter  to  a 
friend,  dated  February  23d,  1668-9,  a  letter  which  is 
also  remarkable  for  containing  the  first  allusion  to 
his  discoveries  respecting  colours.  Previous  to  this 
he  was  in  correspondence  on  the  subject  with  Mr. 
Ent,  afterward  Sir  George  Ent,  one  of  the  original 
council  of  the  Royal  Society,  an  eminent  medical 
writer  of  his  day,  and  President  of  the  College  of- 
Physicians.  In  a  letter  to  Mr.  Ent  he  had  promised 
an  account  of  his  telescope  to  their  mutual  friend, 
and  the  letter  to  which  we  now  allude  contained  tne 
fulfilment  of  that  promise.  The  telescope  was  six 
inches  long.  It  bore  an  aperture  in  the  large  specu- 
lum something  more  than  an  inch,  and  as  the  eye- 
glass was  a  plano-convex  lens,  whose  focal  length 
was  one-sixth  or  one-seventh  of  an  inch,  it  magni- 
fied about  forty  times,  which,  as  Newton  remarks, 
was  more  than  any  six-foot  tube  (meaning  refracting 
telescopes)  could  do  with  distinctness.  On  account 
of  the  badness  of  the  materials,  however,  and  the 
want  of  a  good  polish,  it  represented  objects  less 
distinct  than  a  six-feet  tube,  though  h3  still  thought 
it  would  be  equal  to  a  three  or  four  feet  tube  di- 
rected to  common  objects.  He  had  seen  through  it 
Jupiter  distinctly  with  his  four  satellites,  and  also 
the  horns  or  moon-like  phases  of  Venus,  though  this 
last  phenomenon  required  some  niceness  in  adjusting 
the  instrument. 

Although  Newton  considered  this  little    instru- 


in  the  midst  of  fne  object-glass,  to  transmit  the  light  to  an  eye-glass 
placed  behind  it,  I  had  thence  an  occasion  of  considering  that  sort  of  con- 
struction, and  found  their  disadvantages  so  great,  that  I  saw  it  necessary 
before  I  attempted  any  thing  in  the  practice  to  alter  the  design  of  them 
and  place  the  eye-glass  at  the  side  of  the  tube  rather  than  at  the  middle. 


REFLECTING    TELESCOPE.  89, 

it  as  in  itself  contemptible,  yet  he  regarded  it  as 
an  u  epitome  of  what  might  be  done ;"  and  he  ex- 
pressed his  conviction  that  a  six-feet  telescope  might 
be  made  after  this  method,  which  would  perform  as 
well  as  a  sixty  or  a  hundred  feet  telescope  made  in 
the  common  way;  and  that  if  a  common  refracting 
;elescope  could  be  made  of  the  "purest  glass  exqui- 
sitely polished,  with  the  best  figure  that  any  geo- 
metrician (Descartes,  &c.)  hath  or  can  design,"  it 
would  scarcely  perform  better  than  a  common  tele- 
scope. This,  he  adds,  may  seem  a  paradoxical  as- 
iertion,  yet  he  continues,  "  it  is  the  necessary  con- 
sequence of  some  experiments  which  I  have  made 
concerning  the  nature  of  light."  • 

The  telescope  now  described  possesses  a  very  pe- 
culiar interest,  as  being  the  first  reflecting  one  which 
was  ever  executed  and  directed  to  the  heavens, 
ames  Gregory,  indeed,  had  attempted,  in  1664  or 
665,  to  construct  his  instrument.  He  employed 
Messrs.  Rives  and  Cox,  who  were  celebrated  glass- 
Tinders  of  that  time,  to  execute  a  concave  speculum 
f  six  feet  radius,  and  likewise  a  small  one;  but  as 
hey  had  failed  in  polishing  the  large  one,  and  as  Mr. 
~  regory  was  on  the  eve  of  going  abroad,  he  troubled 
limself  no  farther  about  the  experiment,  and  the 
ube  of  the  telescope  was  never  made.  Some  time 
afterward,  indeed,  he  "  made  some  trials  both  with  a 
ittle  concave  and  convex  speculum,"  but,  "pos^- 
iessed  with  the  fancy  of  the  defective  figure,  hi 
would  not  be  at  the  pains  to  fix  every  thing  in  its  due 
Listance." 

Such  were  the  earliest  attempts  to  construct  the 
eflecting  telescope,  that  noble  instrument  which 
las  since  effected  such  splendid  discoveries  in  as- 
ronomy.  Looking  back  from  the  present  advanced 
itate  of  practical  science,  how  great  is  the  contrast 
>etween  the  loose  specula  of  Gregory  and  the  fine 
Gregorian  telescopes  of  Hadley,  Short,  and  Veitch, 
-—between  the  humble  six-inch  tube  of  Newton  and 
the  gigantic  instruments  of  Herschel  and  Ramage. 


40  SIR   ISAAC   NEWTON. 

The  success  of  this  first  experiment  inspired  New- 
ton with  fresh  zeal,  and  though  his  mind  was  now 
occupied  with  his  optical  discoveries,  with  the  ele- 
ments of  his  method  of  fluxions,  and  with  the  ex- 
panding germ  of  his  theory  of  universal  gravitation, 
yet  with  all  the  ardour  of  youth  he  applied  himself 
to  the  laborious  operation  of  executing  another  re- 
flecting telescope  with  his  own  hands.  This  instru- 
ment, which  was  better  than  the  first,  though  it  lay 
by  him  several  years,  excited  some  interest  at  Cam- 
bridge ;  and  Sir  Isaac  himself  informs  us,  that  one 
of  the  fellows  of  Trinity  College  had  completed  a 
telescope  of  the  same  kind,  which  he  considered  as 
somewhat  superior  to  his  own.  The  existence  of 
these  telescopes  having  become  known  to  the  Royal 
Society,  Newton  was  requested  to  send  his  instru- 
ment for  examination  to  that  learned  body.  He  ac- 
cordingly transmitted  it  to  Mr.  Oldenburg  in  Decem- 
ber, 1671,  and  from  this  epoch  his  name  began  to 
acquire  that  celebrity  by  which  it  has  been  so  pecu- 
liarly distinguished. 

On  the  llth  of  January,  1672,  it  was  announced 
to  the  Royal  Society  that  his  reflecting  telescope 
had  been  shown  to  the  king,  and  had  been  examined 
"by  the  president,  Sir  Robert  Moray,  Sir  Paul  Neale, 
Sir  Christopher  Wren,  and  Mr,  Hook.  These  gen- 
tlemen entertained  so  high  an  opinion  of  it,  that,  in 
qjder  to  secure  the  honour  of  the  contrivance  to  its 
author,  they  advised  the  inventor  to  send  a  drawing 
and  description  of  it  to  Mr.  Huygens  at  Paris.  Mr. 
Oldenburg  accordingly  drew  up  a  description  of  it 
in  Latin,  which,  after  being  corrected  by  Mr.  New- 
ton, was  transmitted  to  that  eminent  philosopher. 
This  telescope,  of  which  the  annexed  is  an  accurate 
drawing,  is  carefully  preserved  in  the  library  of  the 
Royal  Society  of  London,  with  the  following  in- 
scription : — 

"  Invented  by  Sir  Isaac  Newton  and  made  with  his 
own  hands  1671." 


REFLECTING  TELESCOPES. 


41 


42  SIR  ISAAC   NEWTOX. 

It  does  not  appear  that  Newton  executed  any  other 
reflecting  telescopes  than  the  two  we  have  mentioned. 
He  informs  us  that  he  repolished  and  greatly  im- 
proved a  fourteen-feet  object-glass,  executed  by  a 
London  artist,  and  having  proposed  in  1678  to  sub- 
stitute glass  reflectors  in  place  of  metallic  specula, 
he  tried  to  make  a  reflecting  telescope  on  this 
principle  four  feet  long,  and  with  a  magnifying  power 
of  150.  The  glass  was  wrought  by  a  London  artist, 
and  though  it  seemed  well  finished,  yet,  when  it  was 
quicksilvered  on  its  convex  side,  it  exhibited  all  over 
the  glass  innumerable  inequalities,  which  gave  an 
indistinctness  to  every  object.  He  expresses,  how- 
ever, his  conviction  that  nothing  but  good  work- 
manship is  wanting  to  perfect  these  telescopes,  and 
he  recommends  their  consideration  "  to  the  curious 
in  figuring  glasses." 

For  a  period  of  fifty  years  this  recommendation 
excited  no  notice.  At  last  Mr.  James  Short  of 
Edinburgh,  an  artist  of  consummate  skill,  executed 
about  the  year  1730  no  fewer  than  six  reflecting 
telescopes  with  glass  specula,  three  of  fifteen  inches, 
and  three  of  nine  inches  in  focal  length.  He  found 
it  extremely  troublesome  to  give  them  a  true  figure 
with  parallel  surfaces ;  and  several  of  them  when 
finished  turned  out  useless,  in  consequence  of  the 
veins  which  then  appeared  in  the  glass.  Although 
these  instruments  performed  remarkably  well,  yet 
the  light  was  fainter  than  he  expected,  and  from  this 
cause,  combined  with  the  difficulty  of  finishing  them, 
he  afterward  devoted  his  labours  solely  to  those 
with  metallic  specula. 

At  a  later  period,  in  1822,  Mr.  G.  B.  Airy  of 
Trinity  College,  and  one  of  the  distinguished  suc- 
cessors of  Newton  in  the  Lucasian  chair,  resumed 
the  consideration  of  glass  specula,  and  demonstrated 
that  the  aberration  both  of  figure  and  of  colour 
might  be  corrected  in  these  instruments.  Upon  this 
ingenious  principle  Mr.  Airy  executed  more  than 


REFLECTING  TELESCOPES.         43 

one  telescope,  but  though  the  result  of  the  experi- 
ment was  such  as  to  excite  hopes  of  ultimate  suc- 
cess, yet  the  construction  of  such  instruments  is 
still  a  desideratum  in  practical  science. 

Such  were  the  attempts  which  Sir  Isaac  Newton 
made  to  construct  reflecting  telescopes ;  but  notwith- 
standing the  success  of  his  labours,  neither  the  phi- 
losopher nor  the  practical  optician  seems  to  have 
had  courage  to  pursue  them.  A  London  artist,  in- 
deed, undertook  to  imitate  these  instruments ;  but 
Sir  Isaac  informs  us,  that  "  he  fell  much  short  of 
what  he  had  attained,  as  he  afterward  understood 
by  discoursing  with  the  under  workmen  he  had  em- 
ployed." After  a  long  period  of  fifty  years,  John 
Hadley,  Esq.  of  Essex,  a  Fellow  of  the  Royal  So- 
ciety, began  in  1719  or  1720  to  execute  a  reflecting 
telescope.  His  scientific  knowledge  and  his  manual 
dexterity  fitted  him  admirably  for  such  a  task,  and, 
probably  after  many  failures,  he  constructed  two 
large  telescopes  about  five  feet  three  inches  long, 
one  of  which,  with  a  speculum  six  inches  in  diameter, 
was  presented  to  the  Royal  Society  in  1723.  The 
celebrated  Dr.  Bradley  and  the  Rev.  Mr.  Pound 
compared  it  with  the  great  Huygenian  refractor  123 
feet  long.  It  bore  as  high  a  magnifying  power  as 
the  Huygenian  telescope :  it  showed  objects  equally 
distinct,  though  not  altogether  so  clear  and  bright, 
and  it  exhibited  every  celestial  object  that  had  been 
discovered  by  Huygens, — the  five  satellites  of  Sat- 
urn, the  shadow  of  Jupiter's  satellites  on  his  disk, 
the  black  list  in  Saturn's  ring,  and  the  edge  of  his 
shadow  cast  on  the  ring.  Encouraged  and  instructed 
by  Mr.  Hadley,  Dr.  Bradley  began  the  construction 
of  reflecting  telescopes,  and  succeeded  so  well  that 
he  wo  Aid  have  completed  one  of  them,  had  he  not 
been  obliged  to  change  his  residence.  Some  time 
afterward  he  and  the  Honourable  Samuel  Molyneux 
undertook  the  task  together  at  Kew,  and  attempted 
to  execute  specula  about  twenty-six  inches  in  focal 


44  SIR  ISAAC  NEWTON. 

length ;  but  notwithstanding  Dr.  Bradley's  former 
experience,  and  Mr.  Hadley's  frequent  instructions, 
it  was  a  long  time  before  they  succeeded.  The  first 
good  instrument  which  they  finished  was  in  May, 
1724.  It  was  twenty-six  inches  in  focal  length ;  but 
they  afterward  completed  a  very  large  one  of  eight 
feet,  the  largest  that  had  ever  been  made.  The  first 
of  these  instruments  was  afterward  elegantly  fitted 
up  by  Mr.  Molyneux,  and  presented  to  Ins  majesty 
John  V.  King  of  Portugal. 

The  great  object  of  these  two  able  astronomers 
was  to  reduce  the  method  of  making  specula  to 
such  a  degree  of  certainty  that  they  could  be  manu- 
factured for  public  sale.  Mr.  Hauksbee  had  indeed 
made  a  good  one  about  three  and  a  half  feet  long, 
and  had  proceeded  to  the  execution  of  two  others, 
one  of  six  feet,  and  another  of  twelve  feet  in  focal 
length ;  but  Mr.  Scarlet  and  Mr.  Hearne,  having  re- 
ceived all  the  information  which  Mr.  Molyneux  had 
acquired,  constructed  them  for  public  sale ;  and  the 
reflecting  telescope  has  ever  since  been  an  article  of 
trade  with  every  regular  optician. 

As  Sir  Isaac  Newton  was  at  this  time  President 
of  the  Royal  Society,  he  had  the  high  satisfaction 
of  seeing  his  own  invention  become  an  instrument 
of  public  use,  and  of  great  advantage  to  science, 
and  he  no  doubt  felt  the  full  influence  of  this  triumph 
of  his  skill.  Still,  however,  the  reflecting  telescope 
had  not  achieved  any  new  discovery  in  the  heavens. 
The  latest  accession  to  astronomy  had  been  made 
Dy  the  ordinary  refractors  of  Huygens,  labouring 
under  all  the  imperfections  of  coloured  light ;  and 
this  long  pause  in  astronomical  discovery  seemed 
to  indicate  that  man  had  carried  to  its  farthest  limits 
his  power  of  penetrating  into  the  depths  of  the  uni- 
verse. This,  however,  was  only  one  of  those  sta- 
tionary positions  from  which  human  genius  takes  a 
new  and  a  loftier  elevation.  While  the  English  op- 
ticians were  thus  practising  the  recent  art  of  grinding 


DR.  HEUSCHEL'S  TELESCOPES.  45 

specula,  Mr.  James  Short  of  Edinburgh  was  devot- 
ing to  the  subject  all  the  energies  of  his  youthful 
mind.  In  1732,  and  in  the  22d  year  of  his  age,  he 
began  his  labours,  and  he  carried  to  such  high  per- 
fection the  art  of  grinding  and  polishing  specula,  and 
of  giving  them  the  true  parabolic  figure,  that,  with. 
a  telescope  fifteen  inches  in  focal  length,  he  read  in 
the  Philosophical  Transactions  at  the  distance  of 
500  feet,  and  frequently  saw  the  five  satellites  of 
Saturn  together, — a  power  which  was  beyond  the 
reach  even  of  Hadley's  six-feet  instrument.  The 
celebrated  Maclaurin  compared  the  telescopes  of 
Short  with  those  made  b}^  the  best  London  artists, 
and  so  great  was  their  superiority,  that  his  small 
telescopes  were  invariably  superior  to  larger  ones 
from  London.  In  1742,  after  he  had  settled  as  an 
optician  in  the  metropolis,  he  executed  for  Lord 
Thomas  Spencer  a  reflecting  telescope,  twelve  feet 
in  focal  length,  for  630/. ;  in  1752  he  completed  one  for 
the  King  of  Spain,  at  the  expense  of  1200/. ;  and  a 
short  time  before  his  death,  which  took  place  in 
1768,  he  finished  the  specula  of  the  large  telescope 
which  was  mounted  equatorially  for  the  observatory 
of  Edinburgh  by  his  brother  Thomas  Short,  who  was 
offered  twelve  hundred  guineas  for  it  by  the  King  of 
Denmark. 

Although  the  superiority  of  these  instruments, 
which  were  all  of  the  Gregorian  form,  demonstrated 
the  value  of  the  reflecting  telescope,  yet  no  skilful 
hand  had  yet  directed  it  to  the  heavens  ;  and  it  was 
reserved  for  Dr.  Herschel  to  employ  it  as  an  instru- 
ment of  discovery,  to  exhibit  to  the  eye  of  man  new 
worlds  and  new  systems,  and  to  bring  within  the 
grasp  of  his  reason  those  remote  regions  of  space 
to  which  his  imagination  even  had  scarcely  ventured 
to  extend  its  power.  So  early  as  1774  he  completed 
a  five-feet  Newtonian  reflector,  and  he  afterward 
executed  no  fewer  than  two  hundred  7  feet,  one  hun- 
dred and  fifty  10  feet,  and  eighty  20  feet  specula.  In 


"46  SIR   ISAAC   NEWTON. 

1781  he  began  a  reflector  thirty  feet  long,  and  having 
a  speculum  thirty-six  inches  in  diameter ;  and  under 
the  munificent  patronage  of  George  III.  he  com- 
pleted, in  1789,  his  gigantic  instrument  forty  feet 
long,  with  a  speculum  forty-nine  and  a  half  inches 
in  diameter.  The  genius  and  perseverance  which 
created  instruments  of  such  traiiscendant  magnitude 
were  not  likely  to  terminate  with  their  construction. 
In  the  examination  of  the  starry  heavens,  the  ulti- 
mate object  of  his  labours.  Dr.  Herschel  exhibited 
the  same  exalted  qualifications,  and  in  a  few  years 
he  rose  from  the  level  of  humble  life  to  the  enjoy- 
ment of  a  name  more  glorious  than  that  of  the  sages 
and  warriors  of  ancient  times,  and  as  immortal  as 
the  objects  with  which  it  will  be  for  ever  associated. 
Nor  was  it  in  the  ardour  of  the  spring  of  life  that 
these  triumphs  of  reason  were  achieved.  Dr.  Her- 
schel had  reached  the  middle  of  his  course  before 
his  career  of  discovery  began,  and  it  was  in  the  au- 
tumn and  winter  of  his  days  that  he  reaped  the  full 
harvest  of  his  glory.  The  discovery  of  a  new  planet 
at  the  verge  of  the  solar  system  was  the  first  trophy 
of  his  skill,  and  new  double  and  multiple  stars,  and 
new  nebulae,  and  groups  of  celestial  bodies  were 
added  in  thousands  to  the  system  of  the  universe. 
The  spring-tide  of  knowledge  which  was  thus  let  in 
upon  the  human  mind  continued  for  a  while  to  spread 
its  waves  over  Europe  ;  but  when  it  sank  to  its  ebb  in 
England,  there  was  no  other  bark  left  upon  the  strand 
but  that  of  the  Deucalion  of  Science,  whose  home 
had  been  so  long  upon  its  waters. 

During  the  life  of  Dr.  Herschel,  and  during  the 
reign,  and  within  the  dominions  of  his  royal  patron, 
four  new  planets  were  added  to  the  solar  system, 
but  they  were  detected  by  telescopes  of  ordinary 
power ;  and  we  venture  to  state,  that  since  the  reign 
of  George  III  no  attempt  has  been  made  to  keep 
up  the  continuity  of  Dr.  Herschel's  discoveries. 

Mr.  Herschel,  his  distinguished  son,  has  indeed 


ELECTED   INTO    THE    ROYAL   SOCIETY.  47 

c»  **pleted  more  than  one  telescope  of  considerable 
size ;  Mr.  Ramage,  of  Aberdeen,  has  executed  re- 
flectors rivalling  almost  those  of  Slough  ; — and  Lord 
Oxmantown,  an  Irish  nobleman  of  high  promise,  is 
now  engaged  on  an  instrument  of  great  size.  But 
what  avail  the  enthusiasm  and  the  efforts  of  indi- 
vidual minds  in  the  intellectual  rivalry  of  nations  ? 
When  the  proud  science  of  England  pines  in  obscu- 
rity, blighted  by  the  absence  of  the  royal  favour,  and 
of  the  nation's  sympathy; — when  its  chivalry  fall 
unwept  and  unhonoured ; — how  can  it  sustain  the 
conflict  against  the  honoured  and  marshalled  genius 
of  foreign  lands  ? 


CHAPTER  IV. 

He  delivers  a  Course  of.  Optical  Lectures  at  Cambridge — Is  elected  Fellow 
of  the  Royal  Society — He  communicates  to  them  his  Discoveries  on 
the  different  Refrangibility  and  Nature  of  Light—Popular  Account 
of  them— They  involve  him  in  various  Controversies— His  Dispute 
with  Pardies — Linus — Lucas — Dr.  Hooke  and  Mr.  Huygens—Th* 
Influence  of  these  Disputes  on  the  Mind  of  Newton. 

ALTHOUGH  Newton  delivered  a  course  of  lectures 
on  optics  in  the  University  of  Cambridge  in  the 
years  1669,  1670,  and  1671,  containing  his  principal 
discoveries  relative  to  the  different  refrangibility  of 
light,  yet  it  is  a  singular  circumstance,  that  these 
discoveries  should  not  have  become  public  through 
the  conversation  or  correspondence  of  his  pupils. 
The  Royal  Society  had  acquired  no  knowledge  of 
them  till  the  beginning  of  1672,  and  his  reputation 
;  in  that  body  was  founded  chiefly  on  his  reflecting 
'  telescope.  On  the  23d  December,  1671,  the  cele- 
brated Dr.  Seth  Ward,  Lord  Bishop  of  Sarum,  who  • 
was  the  author  of  several  able  works  on  astronomy, 
and  had  filled  the  astronomical  chair  at  Oxford, 
proposed  Mr.  Newton  as  a  Fellow  of  the  Royal 


48  SIR   ISAAC   NEWTON. 

Society.  The  satisfaction  which  he  derived  from  this 
circumstance  appears  to  have  been  considerable ; 
and  in  a  letter  to  Mr.  Oldenburg,  of  the  6th  January, 
he  says,  "  I  am  very  sensible  of  the  honour  done 
me  by  the  Bishop  of  Sarum  in  proposing  me  a  can- 
didate ;  and  which,  I  hope,  will  be  further  conferred 
upon  me  by  my  election  into  the  Society ;  and  if 
so,  I  shall  endeavour  to  testify  my  gratitude,  by 
communicating  what  my  poor  and  solitary  endeav- 
ours can  effect  towards  the  promoting  your  philo- 
sophical designs."  His  election  accordingly  took 
place  on  the  llth  January,  the  same  day  on  which 
the  Society  agreed  to  transmit  a  description  of  his 
telescope  to  Mr.  Huygens  at  Paris.  The  notice  of 
his  election,  and  the  thanks  of  the  Society  for  the 
communication  of  his  telescope,  were  conveyed  in 
the  same  letter,  with  an  assurance  that  the  Society 
"  would  take  care  that  all  right  should  be  done  him 
in  the  matter  of  this  invention."  In  his  next  letter 
to  Oldenburg,  written  on  the  18th  January,  1671-2, 
he  announces  his  optical  discoveries  in  the  following 
remarkable  manner :  "  1  desire  that  in  your  next 
letter  you  would  inform  me  for  what  time  the  So- 
ciety continue  their  weekly  meetings ;  because  if 
they  continue  them  for  any  time,  I  am  purposing 
them,  to  be  considered  of  and  examined,  an  account 
of  a  philosophical  discovery  which  induced  me  to  the 
making  of  the  said  telescope ;  and  I  doubt  not  but 
will  prove  much  more  grateful  than  the  communica- 
tion of  that  instrument ;  being  in  my  judgment  the 
oddest,  if  not  the  most  considerable  detection  which 
hath  hitherto  been  made  in  the  operations  of  nature." 
This  "  considerable  detection"  was  the  discovery 
of  the  different  refrangibility  of  the  rays  of  light 
which  we  ^ave  already  explained,  and  which  led 
to  the  construction  of  his  reflecting  telescope.  It 
was  communicated  to  the  Royal  Society  in  a  letter 
to  Mr.  Oldenburg,  dated  February  6th,  and  excited 
great  interest  among  its  members.  The  "solemn 


COMMUNICATES   HIS   DISCOVERIES.  49 

thanks"  of  the  meeting  were  ordered  to  be  trans- 
mitted to  its  author  for  his  "very  ingenious  dis- 
course." A  desire  was  expressed  to  have  it  imme- 
diately printed,  both  for  the  purpose  of  having  it 
well  considered  by  philosophers,  and  for  "  securing 
the  considerable  notices  thereof  to  the  author  against 
the  arrogations  of  others ;"  and  Dr.  Seth  Ward, 
Bishop  of  Salisbury,  Mr.  Boyle,  and  Dr.  Hooke 
were  desired  to  peruse  and  consider  it,  and  to  bring 
in  a  report  upon  it  to  the  Society. 

The  kindness  of  this  distinguished  body,  and  the 
anxiety  which  they  had  already  evinced  for  his 
reputation,  excited  on  the  part  of  Newton  a  corres- 
ponding feeling,  and  he  gladly  accepted  of  their  pro- 
posal to  publish  his  discourse  in  the  monthly  num- 
bers in  which  the  Transactions  were  then  given  to 
the  world.  "  It  was  an  esteem,"  says  he,*  "  of  the 
Royal  Society  for  most  candid  and  able  judges  in 
philosophical  matters,  encouraged  me  to  present 
them  with  that  discourse  of  light  and  colours,  which 
since  they  have  so  favourably  accepted  of,  I  do  ear- 
nestly desire  you  to  return  them  my  cordial  thanks. 
I  before  thought  it  a  great  favour  to  be  made  a 
member  of  that  honourable  body;  but  I  am  now 
more  sensible  of  .the  advantages;  for  believe  me, 
sir,  I  do  not  only  esteem  it  a  duty  to  concur  with 
you  in  the  promotion  of  real  knowledge ;  but  a  great 
privilege,  that,  instead  of  exposing  discourses  to  a 
prejudiced  and  common  multitude,  (by  which  means 
many  truths  have  been  baffled  and  lost),  I  may  with 
freedom  apply  myself  to  so  jpdicious  and  impartial 
an  assembly.  A  s  to  the  printing  of  that  letter,  I  am 
satisfied  in  theii  judgment,  or  else  I  should  have 
thought  it  too  straight  and  narrow  for  public  view. 
I  designed  it  only  to  those  that  know  how  to  im- 
prove upon  hints  of  things ;  and,  therefore,  to  spare 
tediousness,  omitted  many  such  remarks  and  ex* 

*  Letter  to  Oldenburg,  February  10, 1671. 
E 


50  SIR  ISAAC  NEWTON. 

periments  as  might  be  collected  by  considering  the 
assigned  laws  of  refractions ;  some  of  which  I  be- 
lieve, with  the  generality  of  men,  would  yet  be 
almost  as  taking  as  any  I  described.  But  yet,  since 
the  Royal  Society  have  thought  it  fit  to  appear  pub- 
licly, 1  leave  it  to  their  pleasure :  and  perhaps  to 
supply  the  aforesaid  defects,  I  may  send  you  some 
more  of  the  experiments  to  second  it  (if  it  be  so 
thought  fit),  in  the  ensuing  Transactions." 

Folio  wing  the  order  which  Newton  himself  adopted, 
we  have,  in  the  preceding  chapter,  given  an  account 
of  the  leading  doctrine  of  the  different  refrangibility 
of  light,  and  of  the  attempts  to  improve  the  reflect- 
ing telescope  which  that  discovery  suggested.  We 
shall  now,  therefore,  endeavour  to  make  the  reader 
acquainted  with  the  other  discoveries  respecting 
colours  which  he  at  this  time  communicated  to  the 
Royal  Society. 

Having  determined,  by  experiments 
already  described,  that  a  beam  of 
white  light,  as  emitted  from  the  sun, 
consisted  of  seven  different  colours, 
which  possess  different  degrees  of 
refrangibility,  he  measured  the  re- 
lative extent  of  the  coloured  sp^es, 
and  found  them  to  have  the  propor- 
tions shown  in  Jig.  4,  which  rep- 
resents the  prismatic  spectrum,  and 
,  u  hich  is  nothing  more  than  an  elon- 
gated image  of  the  sun  produced  by 
the  rays  being  separated  in  different 
degrees  from  their  original  direction, 
the  red  being  refracted  least,  and  the 
violet  most  powerfully. 

If  we  consider  light  as  consisting 
of  minute  particles  of  matter,  we  may 
form  some  notion  of  its  decomposi- 
tion by  the  prism  from  the  following 
popular  illustration.  If  we  take  steel 


Fig.  4. 


Orange 


Yellow 


Green 


Blue 


Indigo 


Violet 


DECOMPOSITION   OF  lIGHT.  51 

filings  of  seven  different  degrees  of  fineness  and 
mix  them  together,  there  are  two  ways  in  which  we 
i  may  conceive  the  mass  to  be  decomposed,  or,  what 
I  is  the  same  thing,  all  the  seven  different  kinds  of 
|  filings  separated  from  each  other.  By  means  of 
[seven  sieves  of  different  degrees  of  fineness,  and  so 
Imade  that  the  finest  will  just  transmit  the  finest 
powder  and  detain  all  the  rest,  while  the  next  in 
fineness  transmits  the  two  finest  powders  and  detains 
all  the  rest,  and  so  on,  it  is  obvious  that  all  the  pow- 
ders may  be  completely  separated  from  each  other. 
If  we  again  mix  all  the  steel  filings,  and  laying  them 
upon  a  table,  hold  high  above  them  a  flat  bar  magnet, 
so  that  none  of  the  filings  are  attracted,  then  if  we 
bring  the  magnet  nearer  and  nearer,  we  shall  come 
to  a  point  where  the  finest  filings  are  drawn  up  to  it. 
These  being  removed,  and  the  magnet  brought 
nearer  still,  the  next  finest  powders  will  be  attracted, 
and  so  on  till  we  have  thus  drawn  out  of  the  mass 
all  the  powders  in  a  separate  state.  We  may  con- 
ceive the  bar  magnet  to  be  inclined  to  the  surface 
of  the  steel  filings,  and  so  moved  over  the  mass, 
that  at  the  end  nearest  to  them  the  heaviest  or 
coarsest  will  be  attracted,  and  all  the  remotest  and 
the  finest  or  ligfflrer  filings,  while  the  rest  are  at- 
tracted to  intermediate  points,  so  that  the  seven 
different  filings  are  not  only  separated,  but  are  found 
adhering  in  separate  patches  to  the  surface  of  the 
flat  magnet.  The  first  of  these  methods,  with  the 
sieves,  may  represent  the  process  of  decomposing 
light,  by  which  certain  rays  of  white  light  are  ab- 
sorbed, or  stifled,  or  stopped  in  passing  through 
bodies,  while  certain  other  rays  are  transmitted. 
The  second  method  may  represent  the  process  of 
decomposing  light  by  refraction,  or  by  the  attraction 
of  certain  rays  farther  from  their  original  direction 
than  other  rays,  and  the  different  patches  of  filings 
upon  the  flat  magnet  may  represent  the  spaces  on 
the  spectrum. 


52  SIR  ISAAC   NEWTON. 

When  a  beam  of  white  light  is  decomposed  into 
the  seven  different  colours  of  the  spectrum,  any 
particular  colour,  when  once  separated  from  the 
rest,  is  not  susceptible  of  any  change,  or  farther 
decomposition,  whether  it  is  refracted  through  prisms 
or  reflected  from  mirrors.  It  may  become  fainter 
or  brighter,  but  Newton  never  could,  by  any  process, 
liter  its  colour  or  its  refrangibility. 

Among  the  various  bodies  which  act  upon  light, 
it  is  conceivable  that  there  might  have  been  some 
which  acted  least  upon  the  violet  rays  and  most 
upon  the  red  rays.  Newton,  however,  found  that 
this  never  took  place ;  but  that  the  same  degree  of 
refrangibility  always  belonged  to  the  same  colour, 
and  the  same  colour  to  the  same  degree  of  refran- 
gibility. 

Having  thus  determined  that  the  seven  different 
colours  of  the  spectrum  were  original  or  simple,  he 
was  led  to  the  conclusion  that  whiteness  or  white 
light  is  a  compound  of  all  the  seven  colours  of  the 
spectrum,  in  the  proportions  in  which  they  are  rep- 
resented in  Jig.  4.  In  order  to  prove  this,  or  what 
is  called  the  recomposition  of  white  light  out  of  the 
seven  colours,  he  employed  three  different  methods. 

When  the  beam  RR  was  sepltated  into  its  ele- 


mentary colours  by  the  prism  ABC,  he  received  the 


RECOMPOSIT10N   Of   LIGHT.  53 

Colours  on  another  prism  BOB',  held  either  close  to 
the  first  or  a  little  behind  it,  and  by  the  opposite  re- 
fraction of  this  prism  they  were  all  refracted  back 
into  a  beam  of  white  light  BW,  which  formed  a 
white  circular  image  on  the  wall  at  W,  similar  to 
what  took  place  before  any  of  the  prisms  were 
placed  in  its  way. 

The  other  method  of  recomposing  white  light 
consisted  in  making  the  spectrum  fall  upon  a  lens  at 
some  distance  from  it.  When  a  sheet  of  white 
paper  was  held  behind  the  lens,  and  removed  to  a 
proper  distance,  the  colours  were  all  refracted  into 
a  circular  spot,  and  so  blended  as  to  reproduce  light 
so  perfectly  white  as  not  to  differ  sensibly  from  the 
direct  light  of  the  sun. 

The  last  method  of  recomposing  white  light  was 
one  more  suited^to  vulgar  apprehension.  It  con- 
sisted in  attempting  to  compound  a  white  by  mix- 
ing the  coloured  powders  used  by  painters.  He 
was  aware  that  such  colours,  from  their  very  nature, 
could  not  compose  a  pure  white ;  but  even  this  im- 
perfection in  the  experiment  he  removed  by  an  in- 
genious device.  Me  accordingly  mixed  one  part  of 
red  lead,  four  parts  of  blue  bice,  and  a  proper  propor- 
tion of  orpiment  and  verdigris.  This  mixture  was 
dun,  like  wood  newly  cut,  or  like  the  human  skin. 
He  now  took  one-third  of  the  mixture  and  rubbed 
it  thickly  on  the  floor  of  his  room,  where  the  sun 
shone  upon  it  through  the  opened  casement,  and  be- 
side it,  in  the  shadow,  he  laid  a  piece  of  white  paper 
of  the  same  size.  "  Then  going  from  them  to  the 
distance  of  twelve  or  eighteen  feet,  so  that  he  could 
not  discern  the  unevenness  of  the  surface  of  the 
powder  nor  the  little  shadows  let  fall  from  the  gritty 
particles  thereof;  the  powder  appeared  intensely 
white,  so  as  to  transcend  even  the  paper  itself  in 
whiteness."  By  adjusting  the  relative  illumination 
of  the  powders  and  the  paper,  he  was  able  to 
make  them  both  appear  of  the  very  same  degree  01 
E2 


64  SIR   ISAAC   NEWTON. 

whiteness.  "For,"  says  he,  "when  I  was  trying 
this,  a  friend  coming  to  visit  me,  I  stopped  him  at 
the  door,  and  before  I  told  him  what  the  colours 
were,  or  what  I  was  doing,  I  asked  him  which  of  the 
two  whites  were  the  best,  and  wherein  they  differed? 
And  after  he  had  at  that  distance  viewed  them  well,  he 
answered,  that  they  were  both  good  whites,  and  that 
he  could  not  say  which  was  best,  nor  wherein  their 
colours  differed."  Hence  Newton  inferred  that 
perfect  whiteness  may  be  compounded  of  different 
colours. 

As  all  the  various  shades  of  colour  which  appear 
in  the  material  world  can  be  imitated  by  intercept- 
ing certain  rays  in  the  spectrum,  and  uniting  all  the 
rest,  and  as  bodies  always  appear  of  the  same  colour 
as  the  light  in  which  they  are  placed,  he  concluded, 
that  the  colours  of  natural  bodies  are  not  qualities 
inherent  in  the  bodies  themselves,  but  arise  from  the 
disposition  of  the  particles  of  each  body  to  stop  or 
absorb  certain  rays,  and  thus  to  reflect  more  copiously 
the  rays  which  are  not  thus  absorbed. 

No  sooner  were  these  discoveries  given  to  the 
world  than  they  were  opposed  with  a  degree  of  viru- 
lence and  ignorance  which  have  seldom  been  com- 
bined in  scientific  controversy.  Unfortunately  for 
Newton,  the  Royal  Society  contained  few  individuals 
of  pre-eminent  talent  capable  of  appreciating  the 
truth  of  his  discoveries,  and  of  protecting  him  against 
the  shafts  of  his  envious  and  ignorant  assailants. 
This  eminent  body,  while  they  held  his  labours  in 
the  highest  esteem,  were  still  of  opinion  that  his 
discoveries  were  fair  subjects  of  discussion,  and 
their  secretary  accordingly  communicated  to  him  all 
the  papers  which  were  written  in  opposition  to  his 
views.  The  first  of  these  was  by  a  Jesuit  named 
Ignatius  Pardies,  Professor  of  Mathematics  at  Cler- 
mont,  who  pretended  that  the  elongation  of  the  sun's 
image  arose  from  the  inequal  incidence  of  the  dif- 
ferent rays  on  the  first  face  of  the  prism,  although 


vv 

le 
bi 


CONTROVERSY  WITH  LINUS.  65 

Newton  Tiad  demonstrated  in  his  own  discourse  that 
this  was  not  the  case.  In  April,  1672,  Newton  trans- 
mitted to  Oldenburg  a  decisive  reply  to  the  animad- 
versions of  Pardies ;  but,  unwilling  to  be  vanquished, 
this  disciple  of  Descartes  took  up  a  fresh  position, 
and  maintained  that  the  elongation  of  the  spectrum 
/might  be  explained  by  the  diffusion  of  light  on  the 
hypothesis  of  Grimaldi,  or  by  the  diffusion  of  undu- 
lations on  the  hypothesis  of  Hook.  Newton  again 
replied  to  these  feeble  reasonings  ;  but  he  contented 
himself  with  reiterating1  his  original  experiments, 
and  confirming  them  by  more  popular  arguments, 
and  the  vanquished  Jesuit  wisely  quitted  the  field. 

Another  combatant  soon  sprung  up  in  the  person 
of  one  Francis  Linus,  a  pt^sician  in  Liege,*  who, 
on  the  6th  October,  1674,  addressed  a  letter  to  a 
friend  in  London,  containing  animadversions  on 
Newton's  doctrine  of  colours.  He  boldly  affirms, 
that  in  a  perfectly  clear  sky  the  image  of  the  sun 
made  by  a  prism  is  never  elongated,  and  that  the 
spectrum  observed  by  Newton  was  not  formed  by 
the  true  sunbeams,  but  by  rays  proceeding  from 
some  bright  cloud.  In  support  of  these  assertions, 
he  appeals  to  frequently  repeated  experiments  on 
the  refractions  and  reflections  of  light  which  he 
had  exhibited  thirty  years  before  to  Sir  Kenelm 
Digby,  "  who  took  notes  upon  them ;"  and  he  un- 
blushingly  states,  that,  if  Newton  had  used  the 
same  industry  as  he  did,  he  would  never  have 
"  taken  so  impossible  a  task  in  hand,  as  to  explain 
the  difference  between  the  length  and  breadth  of 
the  spectrum  by  the  received  laws  of  refraction." 
When  this  letter  was  shown  to  Newton,  he  refused 

*  This  gentleman  was  the  author  of  a  paper  in  the  Philosophical 
Transactions,  entitled  "  Optical  Assertions  concerning  the  Rainbow." 
How  such  a  paper  could  be  published  by  so  learned  a  body  seems  in  the 
present  day  utterly  incomprehensible.  The  dials  which  Linus  erected 
at  Liege,  and  which  were  the  originals  of  those  formerly  in  the  Priory 
Gardens  in  London,  are  noticed  in  the  Philosophical  Transactions  for 
1703.  In  one  of  them  the  hours  were  distinguished  by  touch. 


56  SIR  ISAAC   NEWTON. 

to  answer  it ;  but  a  letter  was  sent  to  Linus  referring 
him  to  the  answer  to  Pardies,  and  assuring  him  that 
the  experiments  on  the  spectrum  were  made  when 
there  was  no  bright  cloud  in  the  heavens.  This 
reply,  however,  did  not  satisfy  the  Dutch  experi- 
mentalist. On  the  25th  February,  1675,  he  addressed 
another  letter  to  his  friend,  in  which  he  gravely 
attempts  to  prove  that  the  experiment  of  Newton 
was  not  made  in  a  clear  day ; — that  the  prism  was 
not  close  to  the  hole, — and  that  the  length  of  the 
spectrum  was  not  perpendicular,  or  parallel  to  the 
length  of  the  prism.  Such  assertions  could  not  but 
irritate  even  the  patient  mind  of  Newton.  He  more 
than  once  declined  the  earnest  request  of  Oldenburg 
to  answer  these  observations;  he  stated,  that,  as 
the  dispute  referred  to  matters  of  fact,  it  could  only 
be  decided  before  competent  witnesses,  and  he 
referred  to  the  testimony  of  those  who  had  seen 
his  experiments.  The  entreaties  of  Oldenburg,  how- 
ever, prevailed  over  his  own  better  judgment,  and, 
"lest  Mr.  Linus  should  make  the  more  stir,"  this 
great  man  was  compelled  to  draw  up  a  long  and 
explanatory  reply  to  reasonings  utterly  contempti- 
ble, and  to  assertions  altogether  unfounded.  This 
answer,  dated  November  13th,  1675,  could  scarcely 
have  been  perused  by  Linus,  who  was  dead  on  the 
15th  December,  when  his  pupil  Mr.  Gascoigne,  took 
up  the  gauntlet,  and  declared  that  Linus  had  shown 
to  various  persons  in  Liege  the  experiment  which 
proved  the  spectrum  to  be  circular,  and  that  Sir 
Isaac  could  not  be  more  confident  on  his  side 
than  they  were  on  the  other.  He  admitted,  how- 
ever, that  the  different  results  might  arise  from  dif- 
ferent ways  of  placing  the  prism.  Pleased  with  the 
"  handsome  genius  of  Mr.  Gascoigne's  letter,"  New 
ton  replied  even  to  it,  and  suggested  that  the  spec- 
trum seen  by  Linus  may  have  been  the  circular  one 
formed  by  one  reflexion,  or,  what  he  thought  more 
probable,  the  circular  one  formed  by  two  refraction^ 


CONTROVERSY  WITH   LUCAS.  57 

and  one  intervening  reflection  from  the  base  of  the 
prism,  which  would  be  coloured  if  the  prism  was 

|  not  an  isosceles  o^d.     This   suggestion  seems  to 

t  have  enlightened  the  Dutch  philosophers.  Mr.  Gas- 
coigne,  having  no  conveniences  for  making  the  ex- 

(  periments  pointed  out  by  Newton,  requested  Mr. 
Lucas  of  Liege  to  perform  them  in  his  own  house. 
This  ingenious  individual,  whose  paper  gave  great 
satisfaction  to  Newton,  and  deserves  the  highest 
praise,  confirmed  the  leading  results  of  the  English 

i  philosopher ;  but  though  the  refracting  angle  of  his 
prism  was  60°  and  the  refractions  equal,  he  never 
could  obtain  a  spectrum  whose  length  was  more 
thar.  from  three  to  three  and  a  half  times  its  breadth, 
while  Newton  found  the  length  to  be  Jive  times  its 
breadth.  In  our  author's  reply,  he  directs  his  atten- 
tion principally  to  this  point  of  difference.  He 
repeated  his  measures  with  each  of  the  three  angles 
of  three  different  prisms,  and  he  affirmed  that  Mr. 
Lucas  might  make  sure  to  find  the  image  as  long  or 
longer  than  he  had  yet  done,  by  taking  a  prism  with 
plain  surfaces,  and  with  an  angle  of  66°  or  67°. 
He  admitted  that  the  smallness  of  the  angle  in  Mr. 
Lucas's  prism,  viz.  60°,  did  not  account  for  the 
shortness  of  the  spectrum  which  he  obtained  with 
it ;  and  he  observed  in  one  of  his  own  prisms  that 
the  length  of  the  image  was  greater  in  proportion 
to  the  refracting  angle  than  it  should  have  been ;  an 
effect  which  he  ascribes  to  its  having  a  greater 
refractive  power.  There  is  every  reason  to  believe 
that  the  prism  of  Lucas  had  actually  a  less  disper- 
sive power  than  that  of  Newton ;  and  had  the  Dutch 
philosopher  measured  its  refractive  power  instead 
of  guessing  it,  or  had  Newton  been  less  confident 
than  he  was*  that  all  other  prisms  must  give  a 

*  Newton  speaks  with  singular  positiveness  on  this  subject.  "  For  / 
know"  says  he,  "that  Mr.  Lucas's  observations  cannot  hold  where  the 
refracting  angle  of  the  prism  is  full  60°,  and  the  day  is  clear,  and  the 
fall  length  of  the  colours  is  measured,  and  the  breadth  of  the  image 
answers  to  the  sun's  diameter :  and  seeing  I  am  well  assured  of  th* 


58  SIR  ISAAC   NEWTON. 

spectrum  of  the  same  length  as  his  in  relation  to  its 
refracting  angle  and  its  index  of  refraction,  the  in- 
vention of  the  achromatic  telescope  would  have 
been  the  necessary  result.  The  objections  of  Lucas 
drove  our  author  to  experiments  which  he  had  never 
before  made, — to  measure  accurately  the  lengths  of 
the  spectra  with  different  prisms  of  different  angles 
and  different  refractive  powers ;  and  had  the  Dutch 
philosopher  maintained  his  position  with  more  ob- 
stinacy, he  would  have  conferred  a  distinguished 
favour  upon  science,  and  would  have  rewarded 
Newton  for  all  the  vexation  which  had  sprung  from 
the  minute  discussion  of  his  optical  experiments. 

Such  was  the  termination  of  his  disputes  with  the 
Dutch  philosophers,  and  it  can  scarcely  be  doubted 
that  it  cost  him  more  trouble  to  detect  the  origin  of 
his  adversaries'  blunders,  than  to  establish  the  great 
truths  which  they  had  attempted  to  overturn. 

Harassing  as  such  a  controversy  must  have  been 
to  a  philosopher  like  Newton,  yet  it  did  not  touch 
those  deep-seated  feelings  which  characterize  the 
noble  and  generous  mind.  No  rival  jealousy  yet 
pointed  the  arguments  of  his  opponents ; — no  charges 
of  plagiarism  were  yet  directed  against  his  personal 
character.  These  aggravations  of  scientific  contro- 
versy, however,  he  was  destined  to  endure ;  and  in 
the  dispute  which  he  was  called  to  maintain  both 
against  Hooke  and  Huygens,  the  agreeable  con- 
sciousness of  grappling  with  men  of  kindred  powers 
was  painfully  imbittered  by  the  personality  and 
jealousy  with  which  it  was  conducted. 

Dr.  Robert  Hooke  was  about  seven  years  older 
than  Newton,  and  was  one  of  the  ninety-eight 
original  or  unelected  members  of  the  Royal  Society., 

truth  and  exactness  of  my  own  observations,  I  shall  be  unwilling  to  fa' 
diverted  by  any  other  experiments  from  having  a  fair  end  made  of  this 
in  the  first  place."  On  the  supposition  that  his  prism  was  one  of  very; 
low  dispersive  power,  Mr.  Lucas  might,  with  perfect  truth,  have  usedi 
the  very  same  language  towards  Newton. 


CHARACTER   OF   DR.   HOOKE.  59 

He  possessed  great  versatility  of  talent,  yet,  though 
his  genius  was  of  the  most  original  cast,  and  his 
acquirements  extensive,  he  had  not  devoted  himself 
with  fixed  purpose  to  any  particular  branch  of 
knowledge.  His  numerous  and  ingenious  inven- 
tions, of  which  it  is  impossible  to  speak  too  highly, 
gave  to  his  studies  a  practical  turn  which  unfitted 
him  for  that  continuous  labour  which  physical  re- 
searches so  imperiously  demand.  The  subjects 
of  light,  however,  and  of  gravitation  seem  to  have 
deeply  occupied  his  thoughts  before  Newton  ap- 
peared in  the  same  field,  and  there  can  be  no  doubt 
that  he  had  made  considerable  progress  in  both  of 
these  inquiries.  With  a  mind  less  divergent  in  its 

Eursuits,  and  more  endowed  with  patience  of  thought, 
e  might  have  unveiled  the  mysteries  in  which  both 
these  subjects  were  enveloped,  and  preoccupied  the 
intellectual  throne  which  was  destined  for  his  rival ; 
but  the  infirm  state  of  his  health,  the  peevishness 
of  temper  which  this  occasioned,  the  number  of 
unfinished  inventions  from  which  he  looked  both 
for  fortune  and  fame,  and,  above  all,  his  inordinate 
love  of  reputation,  distracted  and  broke  down  the 
energies  of  his  powerful  intellect.  In  the  more 
matured  inquiries  of  his  rivals  he  recognised,  and 
often  truly,  his  own  incompleted  speculations ;  and 
when  he  saw  others  reaping  the  harvest  for  which 
he  had  prepared  the  ground,  and  of  which  he  had 
sown  the  seeds,  it  was  not  easy  to  suppress  the 
mortification  which  their  success  inspired.  In  the 
history  of  science,  it  has  always  been  a  difficult  task 
to  adjust  the  rival  claims  of  competitors,  when  the 
one  was  allowed  to  have  completed  what  the  other 
was  acknowledged  to  have  begun.  He  who  com- 
mences an  inquiry,  and  publishes  his  results,  often 
goes  much  farther  than  he  has  announced  to  the 
world,  and,  pushing  his  speculations  into  the  very 
heart  of  the  subject,  frequently  submits  them  to  th& 
ear  of  friendship.  From  the  pedestal  of  his  pub- 


60  SIR  ISAAC   NEWTON. 

lished  labours  his  rival  begins  his  researches,  and 
brings  them  to  a  successful  issue ;  while  he  has  in 
reality  done  nothing  more  than  complete  and  de- 
monstrate the  imperfect  speculations  of  his  prede- 
cessor. To  the  world,  and  to  himself,  he  is  no 
doubt  in  the  position  of  the  principal  discoverer} 
but  there  is  still  some  apology  for  his  rival  when 
he  brings  forward  his  unpublished  labours ;  and  some 
excuse  for  the  exercise  of  personal  feeling,  when  he. 
measures  the  speed  of  his  rival  by  his  own  proximity 
to  the  goal. 

The  conduct  of  Dr.  Hooke  would  have  been 
viewed  with  some  such  feeling,  had  not  his  arro- 
gance on  other  occasions  checked  the  natural  cur- 
rent of  our  sympathy.  When  Newton  presented 
his  reflecting  telescope  to  the  Royal  Society,  Dr. 
Hooke  not  only  criticised  the  instrument  with  undue 
severity,  but  announced  that  he  possessed  an  infal- 
lible method  of  perfecting  all  kinds  of  optical  instru- 
ments, so  that  "  whatever  almost  hath  been  in 
notion  and  imagination,  or  desired  in  optics,  may 
be  performed  with  great  facility  and  truth." 

Hooke  had  been  strongly  impressed  with  the 
belief,  that  light  consisted  "in  the  undulations  of  a 
highly  elastic  medium  pervading  all  bodies;  and, 
guided  by  his  experimental  investigation  of  the  phe- 
nomena of  diffraction,  he  had  even  announced  the 
(;  great  principle  of  interference,  which  has  performed 
'  such  an  important  part  in  modern  science.  Regard- 
ing himself,  therefore,  as  in  possession  of  the  true 
theory  of  light,  he  examined  the  discoveries  of 
Newton  in  their  relation  to  his  own  speculative 
views,  and,  finding  that  their  author  was  disposed  to 
consider  that  element  as  consisting  of  material  par- 
ticles, he  did  not  scruple  to  reject  doctrines  which 
he  believed  to  be  incompatible  with  truth.  Dr. , 
Hooke  was  too  accurate  an  observer  not  to  admit  j 
the  general  correctness  of  Newton's  observations. ; 
He  allowed  the  existence  of  different  refractions, 


CONTROVERSY  WITH  HUYGENS.  61 

the  unchangeableness  of  the  simple  colours,  and  the 
.production  of  white  light  by  the  union  of  all  the 
polours  of  the  spectrum ;  but  he  maintained  that  the 
pifferent  refractions  arose  from  the  splitting  and 
rarefying  of  ethereal  pulses,  and  that  there  are  only 
two  colours  in  nature,  viz.  red  and  violet,  which  pro- 
duce by  their  mixture  all  the  rest,  and  which  are 
themselves  formed  by  the  two  sides  of  a  split  pulse 
or  undulation. 

In  reply  to  these  observations,  Newton  wrote  an 
able  letter  to  Oldenburg,  dated  June  11,  1672,  in 
which  he  examined  with  great  boldness  and  force 
of  argument  the  various  objections  of  his  opponent, 
and  maintained  the  truth  of  his  doctrine  of  colours, 
as  independent  of  the  two  hypotheses  respecting 
the  origin  and  production  of  light.  He  acknow- 
ledged his  own  partiality  to  the  doctrine  of  the 
materiality  of  light ;  he  pointed  out  the  defects  of 
the  undulatory  theory  ;  he  brought  forward  new  ex- 
periments in  confirmati  on  of  his  former  results ; 
and  he  refuted  the  opini  >ns  of  Hooke  respecting  the 
existence  of  only  two  simple  colours.  No  reply 
was  made  to  the  powe  ul  arguments  of  Newton ; 
and  Hooke  contented  h  nself  with  laying  before  the 
Society  his  curious  ob?  ••vations  on  the  colours  of 
soap-bubbles,  and  of  plates  of  air,  and  in  pursuing 
his  experiments  on  the  diffraction  of  light,  which, 
after  an  interval  of  two  years,  he  laid  Tbefore  the 
same  body. 

After  he  had  thus  silenced  the  most  powerful  of 
his  adversaries,  Newton  was  again  called  upon  to 
defend  himself  against  a  new  enemy.  Christian 
Huygens,  an  eminent  mathematician  and  natural 
philosopher,  who,  like  Hooke,  had  maintained  the 
undulatory  theory  of  light,  transmitted  to  Olden- 
burg various  animadversions  on  the  Newtonian  doc- 
trine ;  but  though  his  knowledge  of  optics  was  of 
the  most  extensive  kind,  yet  his  objections  were 
nearly  as  groundless  as  those  of  his  less  enlightened 
F 


62  SIR  ISAAC   NEWTON, 

countryman.  Attached  to  his  own  hypothesis  re- 
specting the  nature  of  light,  namely,  to  the  system 
of  undulation,  he  seems,  like  Dr.  Hooke,  to  have 
regarded  the  discoveries  of  Newton  as  calculated  to 
overturn  it ;  but  his  principal  objections  related  tc 
the  composition  of  colours,  and  particularly  of  white 
light,  which  he  alleged  could  be  obtained  from  the 
union  of  two  colours,  yellow  and  blue.  To  this  and 
^similar  objections,  Newton  replied  that  the  colours 
in  question  were  not  simple  yellows  and  blues,  but 
were  compound  colours,  in  which,  together,  all  the 
colours  of  the  spectrum  were  themselves  blended ; 
and  though  he  evinced  some  strong  traces  of  feeling 
at  being  again  put  upon  his  defence,  yet  his  high 
respect  for  Huygens  induced  him  to  enter  with 
patience  on  a  fresh  development  of  his  doctrine. 
Huygens  felt  the  reproof  which  the  tone  of  this 
answer  so  gently  conveyed,  and  in  writing  to  Olden- 
burg, he  used  the  expression,  that  Mr.  Newton 
"  maintained  his  doctrine  with  some  concern."  To 
this  our  author  replied,  "  As  for  Mr.  Huygens's  ex- 
pression, I  confess  it  was  a  little  ungrateful  to  me, 
to  meet  with  objections  which  had  been  answered 
before,  without  having  the  least  reason  given  me 
why  those  answers  were  insufficient."  But  though 
Huygens  appears  in  this  controversy  as  a  rash 
objector  to  the  Newtonian  doctrine,  it  was  after- 
ward the  fate  of  Newton  to  play  a  similar  part 
against  the  Dutch  philosopher.  When  Huygens 
published  his  beautiful  law  of  double  refraction  in 
Iceland  spar,  founded  on  the  finest  experimental 
analysis  of  the  phenomena,  though  presented  as  a 
result  of  the  undulatory  system,  Newton  not  only 
rejected  it,  but  substituted  for  it  another  law  entirely 
inconsistent  with  the  experiments  of  Huygens,  which 
Newton  himself  had  praised,  and  with  those  of  all 
succeeding  philosophers. 

The  influence  of  these  controversies  on  the  mind 
of  Newton  seems  to  have  been  highly  exciting 


REFRACTING  TELESCOPES.         63 

Even  the  satisfaction  of  humbling  all  his  antago- 
nists he  did  not  feel  as  a  sufficient  compensation 
for  the  disturbance  of  his  tranquillity.  "  1  intend," 
says  he,*  "  to  be  no  farther  solicitous  about  matters 
of  philosophy.  And  therefore  I  hope  you  will  not 
take  it  ill  if  you  find  me  never  doing  any  thing  more 
in  that  kind ;  or  rather  that  you  will  favour  me  in 
my  determination,  by  preventing,  so  far  as  you  can 
conveniently,  any  objections  or  other  philosophical 
letters  that  may  concern  me."  In  a  subsequent  let- 
ter in  1675,  he  says, "  I  had  some  thoughts  of  writing 
a  further  discourse  about  colours,  to  be  read  at  one 
of  your  assemblies  ;  but  find  it  yet  against  the  grain 
to  put  pen  to  paper  any  more  on  that  subject ;"  and 
in  a  letter  to  Leibnitz,  dated  December  the  9th,  1675, 
lie  observes,  "  I  was  so  persectited  with  discussions 
arising  from  the  publication  of  my  theory  of  light, 
that  I  blamed  my  own  imprudence  for  parting  with 
so  substantial  a  blessing  as  my  quiet  to  run  after  a 
shadow." 


CHAPTER  V. 

Mistake  of  Newton  in  supposing  that  the  Improvement  nf  Refracting 
Telescopes  was  hopeless — Mr.  Hall  invents  the  Achromatic  Telescope 
— Principles  of  the  Achromatic  Telescope  explained — //  is  re-invented 
by  Dollond,  and  improved  by  future  Artists — Dr.  Blair's  Aplanatie 
Telescope — Mistakes  in  Newton's  Analysis  of  the  Spectrum — Modern 
Discoveries  respecting  the  Structure  of  the  Spectrum. 

THE  new  doctrines  of  the  composition  of  light, 
and  of  the  difTerent  refrangibility  of  the  rays  which 
compose  it,  having  been  thus  established  upon  an 
impregnable  basis,  it  will  be  interesting  to  take  a 
general  view  of  the  changes  which  they  have  under- 

I  etter  to  Oldenburg  in  1672,  containing  his  first  reply  to  Huygens. 


64  SIR   ISAAC  NEWTON. 

gone  since  the  time  of  Newton,  and  of  their  influ- 
ence on  the  progress  of  optical  discovery. 

There  is  no  fact  in  the  history  of  science  more 
singular  than  that  Newton  should  have  believed 
that  all  bodies  produced  spectra  of  equal  length,  or 
separated  the  red  and  violet  rays  to  equal  distances 
when  the  refraction  of  the  mean  rays  was  the 
same.  This  opinion,  unsupported  by  experiments, 
and  not  even  sanctioned  by  any  theoretical  views, 
seems  to  have  been  impressed  upon  his  mind  with 
all  the  force  of  an  axiom.*  Even  the  shortness  of 
the  spectrum  observed  by  Lucas  did  not  rouse  him 
to  further  inquiry ;  and  when,  under  the  influence 
of  this  blind  conviction  he  pronounced  the  improve- 
ment of  the  refracting  telescope  to  be  desperate,  he 
checked  for  a  long  time  the  progress  of  this  branch 
of  science,  and  furnished  to  future  philosophers  a 
lesson  which  cannot  be  too  deeply  studied. 

In  1729,  about  two  years  after  the  death  of  Sir 
Isaac,  an  individual  unknown  to  science  broke  the 
spell  in  which  the  subject  of  the  spectrum  had  been 
so  singularly  bound.  Mr.  Chester  More  Hall,  of 
More  Hall  in  Essex,  while  studying  the  mechanism 
of  the  human  eye,  was  led  to  suppose  that  tele- 
scopes might  be  improved  by  a  combination  of 
lenses  of  different  refractive  powers,  and  he  actually 
completed  several  object-glasses  upon  this  principle. 
The  steps  by  which  he  arrived  at  such  a  construc- 
tion have  not  been  recorded ;  but  it  is  obvious  that 
he  must  have  discovered  what  escaped  the  sagacity 
of  Newton,  that  prisms  made  of  different  kinds  of 

*  In  an  experiment  made  by  Newton,  he  had  occasion  to  counteract 
the  refraction  of  a  prism  of  glass  by  another  prism  of  water ;  and  had 
he  completed  the  experiment,  and  studied  the  result  of  it,  he  could  not 
have  failed  to  observe  a  quantity  of  uncorrected  colour,  which  would 
haTO  led  him  to  the  discovery  of  the  different  dispersive  powers  of  bodies. 
But  in  order  to  increase  the  refractive  power  of  the  water,  he  mixed 
with  it  a  little  sugar  of  lead,  the  high  dispersive  power  of  which  seems 
to  have  rendered  the  dispersive  power  of  the  water  equal  to  that  of  ihe 
glass,  and  thus  to  have  corrected  the  uncompensated  colour  of  the  glass 
prism. 


ACHROMATIC    TELESCOPE. 


66 


produced  different  degrees  of  separation  of  the 
red  and  violet  rays,  or  gave  spectra  of  different 
lengths  when  the  refraction  of  the  middle  ray  of  the 
spectrum  was  the  same. 

In  order  to  explain  how  such  a  property  led  him 
to  the  construction  of  a  telescope  without  colour,  or 
an  achromatic  telescope,  let  us  take  a  lens  LL  of 
crown  or  plate  glass,  whose  focal  length  LY  is 
about  twelve  inches.  When  the  sun's  rays  SL, 


Fig.  6. 


SL  fall  upon  it,  the  red  will  be  refracted  to  R,  the 
yellow  to  Y,  and  the  violet  to  V.  If  we  now  place 
behind  it  a  concave  lens  II  of  the  same  glass,  and 
of  the  same  focus  or  curvature,  it  will  be  found, 
both  by  experiment  and  by  drawing  the  refracted 
rays,  according  to  the  rules  given  in  elementary 
works,  that  the  concave  glass  //  will  refract  the 
rays  LR,  LR  into  LS',  LS;,  and  the  rays  LV,  LV 
into  LS',  LS'  free  of  all  colour;  but  as  these  rays 
will  be  parallel,  the  two  lenses  will  not  have  a 
focus,  and  consequently  cannot  form  an  image  so 
as  to  be  used  as  the  object-glass  of  a  telescope. 
This  is  obvious  from  another  consideration ;  for 
since  the  curvatures  of  the  convex  and  concave 
lenses  are  the  same,  the  two  put  together  will  be 
exactly  the  same  as  if  they  were  formed  out  of  a 
single  piece  of  glass,  having  parallel  surfaces  like  a 
watch-glass,  so  that  the  parallel  rays  of  light  SL, 
F2 


66  SIR  ISAAC  NEWTON. 

SL  will  pass  on  in  the  same  direction  LS',  LS* 
affected  by  equal  and  opposite  refractions  as  in  a 
piece  of  plane  glass. 

Now,  since  the  convex  lens  LL  separated  the 
white  light  SL,  SL  into  its  component  coloured 
rays,  LV,  LV  being  the  extreme  violet,  and  LR 
LR  the  extreme  red ;  it  follows  that  a  similar  con- 
cave lens  of  the  same  glass  is  capable  of  uniting 
into  white  light  LS',  LS'  rays,  as  much  separated 
as  LV,  LR  are.  Consequently,  if  we  take  a  con- 
cave lens  II  of  the  same,  or  of  a  greater  refractive 
power  than  the  convex  one,  and  having  the  power 
of  uniting  rays  farther  separated  than  LV,  LR  are, 
a  less  concavity  in  the  lens  II  will  be  sufficient  to 
unite  the  rays  LV,  LR  into  a  white  ray  LS' ;  but 
as  the  lens  //  is  now  less  concave  than  the  lens  LL 
is  convex,  the  concavity  will  predominate,  and  the 
uncoloured  rays  LS',  LS'  will  no  longer  be  parallel, 
but  will  converge  to  some  point  0,  where  they  will 
form  a  colourless  or  achromatic  image  of  the  sun. 

The  effect  now  described  may  be  obtained  by 
making  the  convex  lens  LL  of  crown  or  of  plate 
glass,  and  the  concave  one  of  flint  glass,  or  that  of 
which  wineglasses  are  made.  If  the  concave  lens 
//  has  a  greater  refractive  power  than  LL,  which  is 
always  the  case,  the  only  effect  of  it  will  be  to 
make  the  rays  converge  to  a  focus  more  remote 
than  O,  or  to  render  a  less  curvature  necessary  in 
//,  if  O  is  fixed  for  the  focus  of  the  combined  lenses. 

Such  is  the  principle  of  the  achromatic  telescope 
as  constructed  by  Mr.  Hall.  This  ingenious  indi- 
vidual employed  working  opticians  to  grind  his 
lenses,  and  he  furnished  them  with  the  radii  of  the 
surfaces,  which  were  adjusted  to  correct  the  aber- 
ration of  figure  as  well  as  of  colour.  His  invention, 
therefore,  was  not  an  accidental  combination  of  a 
convex  and  a  concave  lens  of  different  kinds  of 
glass,  which  might  have  oeen  made  merely  for  ex- 
periment; but  it  was  a  complete  achromatic  tele- 


ACHROMATIC   TELESCOPES.  67 

scope,  founded  on  a  thorough  knowledge  of  the 
lifferent  dispersive  powers  of  crown  and  flint  glass. 
[t  is  a  curious  circumstance,  however,  in  the  his- 
;ory  of  the  telescope,  that  this  invention  was  ac- 
tually lost.  Mr.  Hall  never  published  any  account 
(}f  his  labours,  and  it  is  probable  that  he  kept  them 
secret  till  he  should  be  able  to  present  his  instru- 
nent  to  the  public  in  a  more  perfect  form ;  and  it 
,vas  not  till  John  Dollond  had  discovered  the  pro- 
perty of  light  upon  which  the  instrument  depends, 
md  had  actually  constructed  many  fine  telescopes, 
;hat  the  previous  labours  of  Mr.  Hall  were  laid  be- 
bre  the  public.*  From  this  period  the  achromatic 
elescope  underwent  gradual  improvement,  and  by 
he  successive  labours  of  Dollond,  Ramsden,  Blair, 
Pulley,  Guinand,  Lerebours,  and  Fraunhofer,  it  has 
>ecome  one  of  the  most  valuable  instruments  in. 
)hysical  science. 

Although  the  achromatic  telescope,  as  constructed 
>y  Dollond,  was  founded  on  the  principle  that  the 
spectra  formed  by  crown  and  flint  glass  differed 
mly  in  their  relative  lengths,  when  the  refraction 
)f  the  mean  ray  was  the  same,  yet  by  a  more  mi- 
lute  examination  of  the  best  instruments,  it  was 
bund  that  they  exhibited  white  or  luminous  objects 
inged  on  one  side  with  a  green  fringe,  and  on  the 
Hher  with  one  of  a  claret  colour.  These  colours, 
tvhich  did  not  arise  from  any  defect  of  skill  in  the 
.rtist,  were  found  to  arise  from  a  difference  in  the 
extent  of  the  coloured  spaces  in  two  equal  spectra 
'ormed  by  crown  and  by  flint  glass.  This  property 
was  called  the  irrationality  of  the  coloured  spaces, 
and  the  uncorrected  colours  which  remained  when 
;he  primary  spectrum  of  the  crown  glass  was  cor* 
rected  by  the  primary  spectrum  of  the  flint  glass 
were  called  the  secondary  or  residual  spectrum.  By 

*  See  the  article  OPTICS  in  the  Edinburgh  Encyclopedia,  vol  xv 
»  479,  note. 


68  SIR  ISAAC   NEWTON. 

a  happy  contrivance,  which  it  would  be  out  of  placi 
here  to  describe,  Dr.  Blair  succeeded  in  correcting 
this  secondary  spectrum,  or  in  removing  the  greer 
and  claret-coloured  fringes  which  appeared  in  th< 
best  telescopes,  and  to  this  contrivance  he  gave  the 
name  of  the  Aplanatic  Telescope. 

But  while  Newton  thus  overlooked  these  remark 
able  properties  of  the  prismatic  spectrum,  as  formec 
by  different  bodies,  he  committed  some  considera- 
ble mistakes  in  his  examination  of  the  spectrurr 
which  was  under  his  own  immediate  examination 
It  does  not  seem  to  have  occurred  to  him  that  the 
relations  of  the  coloured  spaces  must  be  greatly 
modified  by  the  angular  magnitude  of  the  sun  or  the 
luminous  body,  or  aperture  from  which  the  spec- 
trum is  obtained ;  and  misled  by  an  apparent  ana- 
logy between  the  length  of  the  coloured  spaces  anc 

,the  divisions  of  a  musical  chord,*  he  adopted  the 

'j:  latter,  as  representing  the  proportion  of  the  col- 
oured spaces  in  every  beam  of  white  light.  Hac 
two  other  observers,  one  situated  in  Mercury,  anc 
the  other  in  Jupiter,  studied  the  prismatic  spectrurr. 
of  the  sun  by  the  same  instruments,  and  with  the 
same  sagacity  as  Newton,  it  is  demonstrable  thai 
they  would  have  obtained  very  different  results.  Or 
account  of  the  apparent  magnitude  of  the  sun  in  Mer- 
cury, the  observer  there  would  obtain  a  spectrum 
entirely  without  green,  having  red,  orange,  and  yel- 

>low  at  one  end,  the  white  in  the  middle,  and  termi- 
nated at  the  other  end  with  blue  and  violet.  The 

'observer  in  Jupiter  would,  on  the  contrary,  have 
obtained  a  spectrum  in  which  the  colours  were 
much  more  condensed.  On  the  planet  Saturn  a 
spectrum  exactly  similar  would  have  been  obtained, 

*"This  result  was  obtained,"  as  Newton  says,  "by  an  assistanl 
whose  eyes  were  more  critii  al  than  mine,  and  who,  by  right  lines  drawn 
across  the  spectrum,  noted  the  confines  of  the  colours.  And  this  opera- 
tion being  divers  times  repeated  both  on  the  same  and  on  several  papers, 
I  found  that  the  observations  agreed  well  enough  with  one  another."— 
OPTICS,  Part  II.  Book  III. 


PRISMATIC    SPECTRUM.  69 

withstanding  the  greater  diminution  of  the  sun's 
[apparent  diameter*  It  may  now  be  asked,  which  of 
all  these  spectra  are  we  to  consider  as  exhibiting 
the  number,  and  arrangement,  and  extent  of  the 
coloured  spaces  proper  to  be  adopted  as  the  true 
[analysis  of  a  solar  ray. 

The  spectrum  observed  by  Newton  has  surely  no 
claim  to  our  notice,  merely  because  it  was  observed 
upon  the  surface  of  the  earth.     The  spectrum  ob- 
tained in  Mercury  affords  no  analysis  at  all  of  the 
incident  beam,  the  colours  being  almost  all  com- 
pound, and  not  homogeneous,  and  that  of  Newton 
is  liable  to  the  same  objection.     Had  Newton  ex- 
amined his  spectrum  under  the  very  same  circum- 
stances in  winter  and  in  summer,  he  would  have 
found  the  analysis  of  the  beam  more  complete  in 
summer,  on  account  of  the  diminution  of  the  sun's 
diameter ;  and,  therefore,  we  are  entitled  to  say  that  i 
neither  the  number  nor  the  extent  of  the  coloured/ 
spaces,  as  given  by  Newton,  are  those  which  belong! 
fohomogeneous  and  uncompoundedjight.  [ 

'I'tie  spectrum  obtained  in  Jupiter  and  Saturn  is 
the  only  one  where  the  analysis  is  complete,  as  it  is 
incapable  of  having  its  character  altered  by  any  far- 
ther diminution  of  the  sun's  diameter.  Hence  we 
are  forced  to  conclude,  not  only  that  the  number 
and  extent  of  the  primitive  homogeneous  colours, 
as  given  by  Newton,  are  incorrect ;  but  that  if  he  had 
attempted  to  analyze  some  of  the  primitive  tints  in 
the  spectrum,  he  would  have  found  them  decidedly 
composed  of  heterogeneous  rays.  There  is  one 
consequence  of  these  observations  which  is  some- 
what interesting.  A  rainbow  formed  in  summer, 
when  the  sun's  diameter  is  least,  must  have  its  col- 
ours more  condensed  and  homogeneous  than  in  win- 
ter, when  the  size  of  its  disk  is  a  maximum,  and 
when  the  upper  or  the  under  limb  of  the  sun  is 
eclipsed,  a  rainbow  formed  at  that  time  will  lose 
entirely  the  yellow  rays,  and  have  the  green  and  the 


70  SIR   ISAAC   NEWTON. 

red  in  perfect  contact.  For  the  same  reason,  a  rain-  ] 
bow  formed  in  Venus  and  Mercury  will  be  destitute 
of  green  rays,  and  have  a  brilliant  bow  of  white 
light  separating  two  coloured  arches ;  while  in  Mars 
Jupiter,  Saturn,  and  the  Georgian  planet,  the  bo\\ 
will  exhibit  only  four  homogeneous  colours. 

From  his  analysis  of  the  solar  spectrum,  Newtor 
concluded, "  that  to  the  same  degree  of  refrangibilit} 
ever  belonged  the  same  colour,  and  to  the  same 
colour  ever  belonged  the  same  degree  of  refrangi- 
bility ;"  and  hence  he  inferred,  that  red,  orange,  yel- 
low, green,  blue,  indigo,  and  violet  were  primary  and. 
simple  colours.  He  admitted,  indeed,  that  "the 
same  colours  in  specie  with  these  primary  ones  ma); 
be  also  produced  by  composition.  For  a  mixture  of 
yellow  and  blue  makes  green,  and  of  red  and  yellou 
makes  orange;"  but  such  compound  colours  were 
easily  distinguished  from  the  simple  colours  of  the 
spectrum  by  the  circumstance,  that  they  are  always 
capable  of  being  resolved  by  the  action  of  the  prism 
into  the  two  colours  which  compose  them. 

This  view  of  the  composition  of  the  spectrum 
might  have  long  remained  unchallenged,  had  we  not 
been  able  to  apply  to  it  a  new  mode  of  analysis. 
Though  we  cannot  separate  the  green  rays  of  the 
spectrum  into  yellow  and  blue  by  the  refraction  of 

grisms,  yet  if  we  possessed  any  substance  which 
ad  a  specific  attraction  for  blue  rays,  and  which 
stopped  them  in  their  course,  and  allowed  the  yel- 
low rays  to  pass,  we  should  thus  analyze  the  green 
as  effectually  as  if  they  were  separated  by  refraction. 
The  substance  which  possesses  this  property  is  a 
purplish  blue  glass,  similar  to  that  of  which  finger- 
glasses  are  made.  When  we  view  through  a  piece 
of  this  glass,  about  the  twentieth  of  an  inch  thick, 
a  brilliant  prismatic  spectrum,  we  find  that  it  has 
exercised  a  most  extraordinary  absorptive  action  on 
the  different  colours  which  compose  it.  The  red 
part  of  the  spectrum  is  divided  into  two  red  spaces^ 


SPECTRUM  OF  THREE  COLOURS.       71 

separated  by  an  interval  entirely  devoid  of  light. 
e  Next  to  the  inner  red  space  comes  a  space  of  bright 
oi/ellow,  separated  from  the  red  by  a  visible  interval. 
;,  A.fter  the  yellow  comes  the  gr&m,  with  an  obscure 
rjspace  between  them,  then  follows  the  blue  and  the 
biolet,  the  last  of  which  has  suffered  little  or  no 
Diminution.     Now  it  is  very  obvious,  that  in  this 
Jbxperiment,  the  blue  glass  has  actually  absorbed 
phe  red  rays,  which,  when  mixed  with  the  yellow 
an  one  side,  constituted  orange,  and  the  blue  rays, 
which,  when  mixed  with  the  yellow  on  the  other 
side,  constituted  green,  so  that  the  insulation  of 
;he  yellow  rays  thus  effected,  and  the  disappearance 
)f  the  orange,  and  of  the  greater  part  of  the  green 
light,  proves  beyond  a  doubt  that  the  orange  and 
rreen  colours  in  the  spectrum  are  compound  col- 
>urs,  the  former  consisting  of  red  and  yellow  rays, 
md  the  latter  of  yellow  and  blue  rays  of  the  very 
ame  refrangibility.      If  we   compare  the  two  red 
spaces  of  the  spectrum  seen  through  the  blue  glass 
kvith  the  red  space  seen  without  the  blue  glass,  it 
vill  be  obvious  that  the  red  has  experienced  such 
in  alteration  in  its  tint  by  the  action  of  the  blue 
flass,  as  would  be  effected  by  the  absorption  of  a 
imall  portion  of  yellow  rays ;   and  hence  we  con- 
dude,  that  the  red  of  the  spectrum  contains  a  slight 
inge  of  yellow,  and  that  the  yellow  space  extends 
>ver  more  than  one-half  of  the  spectrum,  including 
he  red,  orange,  yellow,  green,  and  blue  spaces. 

I  have  found  also  that  red  light  exists  in  the  yel- 
ow  space,  and  it  is  certain  that  in  the  violet  space 
ed  light  exists  in  a  state  of  combination  with  the 
)lue  rays.  From  these  and  other  facts  which  it 
ivould  be  out  of  place  here  to  explain,  I  conclude 
hat  the  prismatic  spectrum  consists  of  three  differ- 
nt  spectra,  viz.  red,  yellow,  and  blue,  all  having 
he  same  length,  and  all  overlapping  each  other. 
Hence  red,  yellow,  and  blue  rays  of  the  very  same 
efrangibility  coexist  at  every  point  of  the  spec* 


72  em  ISAAC  NEWTON. 

trum ;  but  the  colour  at  any  one  point  will  be  thai 
of  the  predominant  ray,  and  will  depend  upon  the 
relative  distance  of  the  point  from  the  maximum 
ordinate  of  the  curve  which  represents  the  intensity 
of  the  light  of  each  of  the  three  spectra. 

This  structure  of  the  spectrum,  which  harmo- 
nizes with  the  old  hypothesis  of  three  simple  colours, 
will  be  understood  from  the  annexed  diagram 
where  MN  is  the  spectrum  of  seven  colours,  al 
compounded  of  the  three  simple  ones,  red,  yellow 

Fig.  7. 


and  blue.  The  ordinates  of  the  curves  R,  Y,  anc 
B  will  express  the  intensities  of  each  colour  at  dif- 
ferent points  of  the  spectrum.  At  the  red  extrem- 
ity M  of  the  spectrum,  the  pure  red  is  scarcel} 
altered  by  the  very  slight  intermixture  of  yellow 
and  blue.  Farther  on  in  the  red  space,  the  yellou 
begins  to  make  the  red  incline  to  scarlet.  It  ther 
exists  in  sufficient  quantity  to  form  orange,  and,  as 
the  red  declines,  the  yellow  predominates  over  the 
feeble  portion  of  red  and  blue  which  are  mixed  wit! 
it.  As  the  yellow  decreases  in  intensity,  the  in- 
creasing  blue  forms  with  it  a  good  green,  and  the 
blue  rising  to  its  maximum  speedily  overpowers  the 
small  portion  of  yellow  and  red.  When  the  blue 
becomes  very  faint,  the  red  exhibits  its  influence 
in  converting  it  into  violet,  and  the  yellow  ceasei 


LIXES   IN   THE   SPECTRtTM.  73 

to  exercise  a  marked  influence  on  the  tint.  The 
influence  of  the  red  over  the  blue  space  is  scarcely 
perceptible,  on  account  of  the  great  intensity  of  the 
blue  light ;  but  we  may  easily  conceive  it  to  reap- 
pear and  form  the  violet  light,  not  only  from  the 
rapid  decline  of  the  blue  light,  but  from  the  greater 
influence  of  the  red  rays  upon  the  retina. 

These  views  may,  perhaps,  be  more  clearly  under- 
stood by  supposing  that  a  certain  portion  of  white 
light  is  actually  formed  at  every  point  of  the  spec- 
trum by  the  union  of  the .  requisite  number  of  the 
three  coloured  rays  that  exist  at  any  point.  The 
white  light  thus  formed  will  add  to  the  brilliancy 
without  affecting  the  tint  of  the  predominant  colour. 

In  the  violet  space  we  may  conceive  the  small 
portion  of  yellow  which  exists  there  to  form  white 
light  with  a  part  of  the  blue  and  a  part  of  the  red, 
so  that  the  resulting  tint  will  be  violet,  composed 
of  the  blue  and  the  small  remaining  portion  of  red, 
mixed  with  the  white  light.  This  white  light  will 
possess  the  remarkable  property  of  not  being  sus- 
ceptible of  decomposition  by  the  analysis  of  the 
prism,  as  it  is  composed  of  red,  yellow,  and  blue 
rays  of  the  very  same  refrangibility.  The  insula- 
tion of  this  white  light  by  the  absorption  of  the 
predominant  colours  I  have  effected  in  the  green, 
yellow,  and  red  spaces,  and  by  the  use  of  new  ab- 
sorbing media  we  may  yet  hope  to  exhibit  it  in  some 
of  the  other  colours,  particularly  in  the  brightest 
part  of  the  blue  space,  where  an  obvious  approxi- 
mation to  it  takes  place. 

:  Among  the  most  important  modern  discoveries 
respecting  the  spectrum  we  must  enumerate  that 
of  fixed  dark  and  coloured  lines,  which  we  owe  to 
the  sagacity  of  Dr.  Wollaston  and  M.  Fraunhofer. 
Two  or  three  of  these  lines  were  discovered  by  Dr. 
Wollaston,  but  nearly  600  have  been  detected  by 
means  of  the  fine  prisms  and  the  magnificent  appa- 
ratus of  the  Bavarian  optician.  These  lines  are 
G 


SIR   ISAAC   NEWTOW. 


parallel  to  one  another,  and  perpendicular  to  the 
length  of  the  spectrum.  The  largest  occupy  a 
space  from  5"  to  10"  in  breadth.  Sometimes  they 
occur  in  well-defined  lines,  and  at  other  times  in 
groups  ;  and  in  all  spectra  formed  from  solar  light, 
they  preserve  the  same  order  and  intensity,  and  the 
same  relative  position  to  the  coloured  spaces,  what- 
ever be  the  nature  of  the  prism  by  which  they  are 
froduced.  Hence  these  lines  are  fixed  points,  by 
which  the  relative  dispersive  powers  of  different 
media  may  be  ascertained  with  a  degree  of  accu- 
racy hitherto  unknown  in  this  branch  of  science.  In 
the  light  of  the  fixed  stars,  and  in  that  of  artificial 
flames,  a  different  system  of  lines  is  produced,  and 
this  system  remains  unaltered,  whatever  be  the  na- 
ture of  the  prism  by  which  the  spectrum  is  formed. 
The  most  important  fixed  lines  in  the  spectrum 
formed  by  light  emitted  from  the  sun,  whether  it  is 
reflected  from  the  sky,  the  clouds,  or  the  moon,  may 
be  easily  seen  by  looking  at  a  narrow  slit  in  the 
window-shutter  of  a  dark  room,  through  a  hollow 
prism  formed  of  plates  of  parallel  glass,  and  filled 
with  any  fluid  of  a  considerable  dispersive  power. 
The  slit  should  not  greatly  exceed  the  twentieth  of 
an  inch,  and  the  eye  should  look  through  the  thinnest 
edge  of  the  prism  where  there  is  the  least  thickness 
of  fluid.  These  lines  I  have  found  to  be  the  boun- 
daries of  spaces  within  which  the  rays  have  par- 
ticular affinities  for  particular  bodies. 


COLOURS  OF  THIN  PLATES.        75 


CHAPTER  VL 

Colours  of  thin  Plates  first  studied  by  Boy  ^and  Hooke — Newton  de- 
termines the  Law  of  their  Production— His  Theory  of  Fits  of  Easy 
Refection  and  Transmission — Colours  of  thick  Plates. 

IN  examining  the  nature  and  origin  of  colours  as 
the  component  parts  of  white  light,  the  attention  of 
Newton  was  directed  to  the  curious  subject  of  the 
colours  of  thin  plates,  and  to  its  application  to  ex- 
plain the  colours  of  natural  bodies.  His  earliest 
researches  on  this  subject  were  communicated,  in 
his  Discourse  on  Light  and  Colours,  to  the  Royal 
Society,  on  the  9th  December,  1675,  and  were  read 
at  subsequent  meetings  of  that  body.  This  discourse 
contained  fuller  details  respecting  the  composition 
and  decomposition  of  light  than  he  had  given  in  his 
letter  to  Oldenburg,  and  was  concluded  with  nine 
propositions,  showing  how  the  colours  of  thin  trans- 
parent plates  stand  related  to  those  of  all  natural 
bodies. 

The  colours  of  thin  plates  seem  to  have  been 
first  observed  by  Mr.  Boyle.  Dr.  Hooke  afterward 
studied  them  with  some  care,  and  gave  a  correct 
account  of  the  leading  phenomena,  as  exhibited  in 
the  coloured  rings  upon  soap-bubbles,  and  between 
plates  of  glass  pressed  together.  He  recognised 
that  the  colour  depended  upon  some  certain  thick- 
ness of  the  transparent  plate,  but  he  acknowledges 
that  he  had  attempted  in  vain  to  discover  the  rela- 
tion between  the  thickness  of  the  plate  and  the 
colour  which  it  produced. 

Dr.  Hooke  succeeded  in  splitting  a  mineral  sub- 
stance, called  mica,  into  films  of  such  extreme  thin- 
ness as  to  give  brilliant  colours.  One  p'ate,  for  ex- 


76  SIR   ISAAC   NEWTON. 

ample,  gave  a  yellow  colour,  another  a  blue  colour, 
and  the  two  together  a  deep  purple ;  but,  as  plates 
which  produced  those  colours  were  always  less  than 
the  12,000th  part  of  an  inch  thick,  it  was  quite  im- 
practicable, by  any  contrivance  yet  discovered,  to 
measure  their  thickness,  and  determine  the  law  ac- 
cording to  which  the  colour  varied  with  the  thick- 
ness of  the  film.  Newton  surmounted  this  difficulty 
by  laying  a  double  convex  lens,  the  radius  of  curva- 
ture of  each  side  of  which  was  fifty  feet,  upon  the 
flat  surface  of  a  plano-convex  object-glass,  and  in 
this  way  he  obtained  a  plate  of  air  or  of  space  vary- 
ing from  the  thinnest  possible  edge  at  the  centre  of 
the  object-glass  where  it  touched  the  plane  surface, 
to  a  considerable  thickness  at  the  circumference  of 
the  lens.  When  light  was  allowed  to  fall  upon  the 
object-glass,  every  different  thickness  of  the  plate 
of  air  between  the  object-glass  gave  different  colours, 
so  that  the  point  where  the  two  object-glasses 
touched  one  another  was  the  centre  of  a  number  of 
concentric  coloured  rings.  Now,  as  the  curvature 
of  the  object-glass  was  known,  it  was  easy  to  cal- 
culate the  thickness  of  the  plate  of  air  at  which  any 
particular  colour  appeared,  and  thus  to  determine 
the  law  of  the  phenomena. 

In  order  to  understand  how  he  proceeded,  let 
CED  be  the  convex  surface  of  the  one  object-glass,  and 
AEB  the  flat  surface  of  the  other.  Let  them  touch 
at  the  point  E,  and  let  homogeneous  red  rays  fall 
upon  them,  as  shown  in  the  figure.  At  the  point 
of  contact  E,  where  the  plate  of  air  is  inconceiva- 
bly thin,  not  a  single  ray  of  the  pencil  RE  is  re- 
flected. The  light  is  wrholly  transmitted,  and,  con- 
sequently, to  an  eye  above  E,  there  will  appear  at 
E  a  black  spot.  At  <z,  where  the  plate  of  air  is 
thicker,  the  red  light  ra  is  reflected  in  the  direction 
ca',  and  as  the  air  has  the  same  thickness  in  a  circle 
round  tho  point  E,  the  eye  above  E,  at  a,  will  see 
next  the  black  spot  E  a  ring  of  red  light.  At  m, 


COLOURS  OF  THIN  PLATES. 

Fig.  8. 


77 


where  the  thickness  of  the  air  is  a  little  greater  than 
at  «,  the  light  r'm  is  all  transmitted  as  at  E,  and  not 
a  single  ray  suffers  reflection,  so  that  to  an  eye 
above  E  at  mf  there  will  be  seen  without  the  red  ring 
a  a  dark  ring  m.  In  like  manner,  at  greater  thick- 
nesses of  the  plate  of  air,  there  is  a  succession  of 
red  and  dark  rings,  diminishing  in  breadth  as  shown 
in  the  diagram. 

When  the  same  experiment  was  repeated  in  orarige, 
yellow,  green,  Uue,  indigo,  and  violet  light,  the  very 
same  phenomenon  was  observed;  with  this  differ- 
ence only,  that  the  rings  were  largest  in  red  light, 
and  smallest  in  violet  light,  and  had  intermediate 
magnitudes  in  the  intermediate  colours. 

If  the  observer  now  places  his  eye  below  E,  so 
as  to  see  the  transmitted  rays,  he  will  observe  a  set 
of  rings  as  before,  but  they  will  have  a  bright  spot 
in  their  centre  at  E,  and  the  luminous  rings  will  now 
correspond  with  those  which  were  dark  when  seen 
by  reflection,  as  will  be  readily  understood  from  in- 
specting the  preceding  diagram. 

When  the  object-glasses  are  illuminated  by  white 
G2 


78  SIR   ISAAC   NEWTON. 

light,  the  seven  systems  of  rings,  formed  by  all  the 
seven  colours  which  compose  white  light,  will  now 
be  seen  at  once.  Had  the  rings  in  each  colour  been 
all  of  the  same  diameter  they  would  all  have  formed 
brilliant  white  rings,  separated  by  dark  intervals; 
but,  as  they  have  all  different  diameters,  they  will 
overlap  one  another,  producing  rings  of  various 
colours  by  their  mixture.  These  colours,  reckoning 
from  the  centre  E,  are  as  follows  :  — 

1st  Order.  Black,  blue,  white,  yellow,  orange,  red. 

2d  Order.  Violet,  blue,  green,  yellow,  orange,  red. 

3d  Order.  Purple,  blue,  green,  yellow,  red,  bluish- 
red. 

4th  Order.  Bluish-green,  green,  yellowish-green, 
red. 

5th  Order.  Greenish-blue,  red. 

6th  Order.  Greenish-blue,  red. 

By  accurate  measurements,  Sir  Isaac  found  that 
the  thicknesses  of  air  at  which  the  most  luminous 
parts  of  the  first  rings  were  produced,  were  in  parts 
of  an  inch  TTf  3-^,  -py^Tnnj?  TT5Tr<nr»  TTffrnnr* 


c  TTf  3-^,  -py^Tnnj?  TT5Tr<nr»  TTffrnnr*  TT^ffw* 
If  tne  niedium  or  the  substance  of  the  thin 
plate  is  water,  as  in  the  case  of  the  soap-bubble, 
which  produces  beautiful  colours  according  to  its 
different  degrees  of  thinness,  the  thicknesses  at 
which  the  most  luminous  parts  of  the  rings  appear 
are  produced  at  j.^  of  the  thickness  at  which  they 
are  produced  in  air,  and  in  the  case  of  glass  or  mica 
atr.?V?  °f  tnat  thickness;  the  numbers  1.336,  1.525 
expressing  the  ratio  of  the  sines  of  the  angles  of 
incidence  and  refraction  in  the  substances  which 
produce  the  colours. 

From  the  phenomena  thus  briefly  described,  Sir 
Isaac  Newton  deduces  that  ingenious,  though  hy- 
pothetical, property  of  light,  called  its  fits  of  easy 
reflection  and  transmission.  This  property  consists  in 
supposing  that  every  particle  of  light  from  its  first 
discharge  from  a  luminous  body  possesses,  at  equally 
distant  intervals,  dispositions  to  be  reflected  from, 


FITS   OF   REFLECTION,  ETC  79 

and  transmitted  through,  the  surfaces  of  bodies  upon 
which  it  is  incident.  Hence,  if  a  particle  of  light 
reaches  a  reflecting  surface  of  glass  when  it  is  in 
its^  of  reflection,  or  in  its  disposition  to  be  reflected, 
it  will  yield  more  readily  to  the  reflecting  force  of 
the  surface ;  and,  on  the  contrary,  if  it  reaches  the 
same  surface  while  in  a  Jit  of  easy  transmission,  or 
in  a  disposition  to  be  transmitted,  it  will  yield  with 
more  difficulty  to  the  reflecting  force.  Sir  Isaac 
has  not  ventured  to  inquire  into  the  cause  of  this 
property ;  but  we  may  form  a  very  intelligible  idea 
of  it  by  supposing,  that  the  particles  of  light  have 
two  attractive  and  two  repulsive  poles  at  the  ex- 
tremities of  two  axes  at  right  angles  to  each  other, 
and  that  the  particles  revolve  round  their  axes,  and 
at  equidistant  intervals  bring  one  or  other  of  these 
axes  into  the  line  of  the  direction  in  which  the  par- 
ticle is  moving.  If  the  attractive  axis  is  in  the  line 
of  the  direction  in  which  the  particle  moves  when  it 
reaches  the  refracting  surface,  the  particle  will  yield 
to  the  attractive  force  of  the  medium,  and  be  re- 
fracted and  transmitted ;  but  if  the  repulsive  axis  is 
in  the  direction  of  the  particle's  motion  when  it 
reaches  the  surface,  it  will  yield  to  the  repulsive 
force  of  the  medium,  and  be  reflected  from  it. 

The  application  of  the  theory  of  alternate  fits  of 
reflection  and  transmission  to  explain  the  colours  of 
thin  plates  is  very  simple.  When  the  light  falls  upon 
the  first  surface  AB,  Fig.  8  of  the  plate  of  air  be- 
tween AB  and  CED,  the  rays  that  are  in  a  fit  of  re- 
flection are  reflected,  and  those  that  are  in  a  fit  of 
transmission  are  transmitted.  Let  us  call  F  the 
length  of  a  fit,  or  the  distance  through  which  the 
particle  of  light  moves  while  it  passes  from  the  state 
of  being  in  a  fit  of  reflection  to  the  state  of  being  in 
a  fit  of  transmission.  Now,  as  all  the  particles  of 
light  transmitted  through  AB  were  in  a  state  of  easy 
transmission  when  they  entered  AB,  it  is  obvious, 
that,  if  the  plate  of  air  at  E  is  so  thin  as  to  be  less 


80  SIR   ISAAC   NEWTON. 

than  one-half  of  F,  the  particles  of  light  will  still 
be  in  their  disposition  to  be  transmitted,  and  conse- 
quently the  light  will  be  all  transmitted,  and  none 
reflected  at  the  curve  surface  at  E.  When  the  plate 
becomes  thicker  towards  0,  so  that  its  thickness  ex- 
ceeds half  of  F,  the  light  will  not  reach  the  surface 
CE  till  it  has  come  under  its  fit  of  reflection,  and 
consequently  at  a  the  light  will  be  all  reflected,  and 
none  transmitted.  As  the  thickness  increases  to- 
wards m,  the  light  will  have  come  under  its  fit  of 
transmission,  and  so  on,  the  light  being  reflected  at 
a,  Z,  and  transmitted  at  E,  m.  This  will  perhaps  be 
still  more  easily  understood  from  fig.  9,  where  we 

Fig.  9. 


may  suppose  AEG  to  be  a  thin  wedge  of  glass  or 
any  other  transparent  body.  When  light  is  incident 
on  the  first  surface  AE,  all  the  particles  of  it  that 
are  in  a  fit  of  easy  reflection  will  be  reflected,  and 
all  those  in  a  fit  of  easy  transmission  will  be  trans- 
mitted. As  the  fits  of  transmission  all  commence 
at  AE,  let  the  first  fit  of  transmission  end  when  the 
particles  of  light  have  reached  ab,  and  the  second 
when  they  have  reached  ef;  and  let  the  fits  of  re- 
flection commence  at  cd  and  gh.  Then,  as  the  fit 
of  transmission  continues  from  AE  to  ab,  all  the 
light  that  falls  upon  the  portion  mE  of  the  second 
surface  will  be  transmitted  and  none  reflected,  so 
that  to  an  eye  above  E  the  space  mE  will  appear 
black.  As  the  fit  of  reflection  commences  at  ab,  and 


COLOURS  OF  THICK  PLATES.        81 

continues  to  cd,  all  the  light  which  falls  upon  the 
portion  nm  will  be  reflected,  and  none  transmitted ; 
and  so  on,  the  light  being  transmitted  at  mE  and 
pn,  and  reflected  at  nm  and  qp.  Hence  to  an  eye 
above  E  the  wedge-shaped  film  of  which  AEG  is 
a  section  will  be  covered  with  parallel  bands  or 
fringes  of  light  separated  by  dark  fringes  of  the 
same  breadth,  and  they  will  be  all  parallel  to  the 
thin  edge  of  the  plate,  a  dark  fringe  corresponding 
10  the  thinnest  edge.  To  an  eye  placed  below  CE 
similar  fringes  will  be  seen,  but  the  one  correspond- 
ing to  the  thinnest  edge  mE  will  be  luminous. 

If  the  thickness  of  the  plate  does  not  vary  accord- 
ing to  a  regular  law  as  in  Jig.  9,  but  if,  like  a  film  of 
blown  glass,  it  has  numerous  inequalities,  then  the 
alternate  fringes  of  light  and  darkness  will  vary  with 
the  thickness  of  the  film,  and  throughout  the  whole 
length  of  each  fringe  the  thickness  of  the  film  will 
be  the  same. 

We  have  supposed  in  the  preceding  illustration 
that  the  light  employed  is  homogeneous.  If  it  is 
white,  then  the  differently  coloured  fringes  will  form 
by  their  superposition  a  system  of  fringes  analogous 
to  those  seen  between  two  object-glasses,  as  already 
explained. 

The  same  periodical  colours  which  we  have  now 
described  as  exhibited  by  thin  plates  were  discov- 
ered by  Newton  in  thick  plates,  and  he  has  ex- 
plained them  by  means  of  the  theory  of  fits ;  but  it 
would  lead  us  beyond  the  limits  of  a  popular  work 
like  this  to  enter  into  any  details  of  his  observations, 
or  to  give  an  account  of  the  numerous  and  important 
additions  which  this  branch  of  optics  has  received 
from  the  discoveries  of  £  deseeding  authors. 


SIR  ISAAC   NEWTON. 


CHAPTER  VII. 

Newton's  Theory  of  the  Colours  of  Natural  Bodies  explained— Objec- 
tions to  it  stated — New  Classification  of  Colours — Outline  of  a  New 
Theory  proposed, 

IP  the  objects  of  the  material  world"  had  been 
illuminated  with  white  light,  all  the  particles  of 
which  possessed  the  same  degree  of  refrangibility, 
and  were  equally  acted  upon  by  the  bodies  on  which 
they  fall,  all  nature  would  have  shone  with  a  leaden 
hue,  and  all  the  combinations  of  external  objects, 
and  all  the  features  of  the  human  countenance,  would 
have  exhibited  no  other  variety  but  that  which  they 
possess  in  a  pencil  sketch  or  a  China-ink  drawing. 
The  rainbow  itself  would  have  dwindled  into  a  nar- 
row arch  of  white  light, — the  stars  would  have  shone 
through  a  gray  sky, — and  the  mantle  of  a  wintry 
twilight  would  have  replaced  the  golden  vesture  of 
the  rising  and  the  setting  sun.  But  He  who  has  ex- 
hibited such  matchless  skill  in  the  organization  of 
material  bodies,  and  such  exquisite  taste  in  the  forms 
upon  which  they  are  modelled,  has  superadded  that 
ethereal  beauty  which  enhances  their  more  per- 
manent qualities,  and  presents  them  to  us  in  the 
ever-varying  colours  of  the  spectrum.  Without  this 
the  foliage  of  vegetable  life  might  have  rilled  the  eye 
and  fostered  the  fruit  which  it  veils, — but  the  youth- 
ful green  of  its  spring  would  have  been  blended  with 
the  dying  yellow  of  its  autumn.  Without  this  the 
diamond  might  have  displayed  to  science  the  beauty 
of  its  forms,  and  yielded  to  the  arts  its  adamantine 
virtues ; — but  it  would  have  ceased  to  shine  in  the 
chaplet  of  beauty,  and  to  sparkle  in  the  diadem  of 
princes.  Without  this  the  human  countenance  might 


COLOURS    OF   NATURAL   BODIES.  83 

have  expressed  all  the  sympathies  of  the  heart,  but 
the  "  purple  light  of  love"  would  not  have  risen  on 
the  cheek,  nor  the  hectic  flush  been  the  herald  of 
its  decay. 

The  gay  colouring-  with  which  the  Almighty  has 
decked  the  pale  marble  of  nature  is  not  the  result 
of  any  quality  inherent  in  the  coloured  body,  or  in 
the  particles  by  which  it  may  be  tinged,  but  is  merely 
a  property  of  the  light  in  which  they  happen  to  be 
Dlaced.  Newton  was  the  first  person  who  placed 
his  great  truth  in  the  clearest  evidence.  He  found 
hat  all  bodies,  whatever  were  their  peculiar  colours, 
exhibited  these  colours  only  in  white  light.  When 
hey  were  illuminated  by  homogeneous  red  light 
hey  appeared  red,  by  homogeneous  yellow  light, 
jellow,  and  so  on,  "  their  colours  being  most  brisk 
and  vivid  under  the  influence  of  their  own  daylight 
colours."  The  leaf  of  a  plant,  for  example,  ap- 
)eared  green  in  the  white  light  of  day,  because  it 
lad  the  property  of  reflecting  that  light  in  greater 
abundance  than  any  other.  When  it  was  placed  in 
lomogeneous  red  light,  it  could  no  longer  appear 
green,  because  there  was  no  green  light  to  reflect ; 
nit  it  reflected  a  portion  of  red  light,  because  there 
was  some  red  in  the  compound  green  which  it  had 
;he  property  of  reflecting.  Had  the  leaf  originally 
reflected  a  pure  homogeneous  green,  unmixed  with 
red,  and  reflected  no  white  light  from  its  outer  sur- 
face, it  would  have  appeared  quite  black  in  pure  ho- 
mogeneous red  light,  as  this  light  does  not  contain 
a  single  ray  which  the  leaf  was  capable  of  reflect- 
ing. Hence  the  colours  of  material  bodies  are  owing 
to  the  property  which  they  possess  of  stopping  cer- 
tain rays  of  white  light,  while  they  reflect  or  trans- 
mit to  the  eye  the  rest  of  the  rays  of  which  white 
light  is  composed. 

So  far  the  Newtonian  doctrine  of  colours  is  ca- 
pable of  rigid  demonstration;  but  its  author  was 
not  content  with  carrying  it  thus  far :  he  sought  to 


84  SIR  ISAAC   NEWTON. 

determine  the  manner  in  which  particular  rays  are 
stopped,  while  others  are  reflected  or  transmitted ; 
and  the  result  of  this  profound  inquiry  was  his  theory 
of  the  colours  of  natural  bodies,  which  was  commu- 
nicated to  the  Royal  Society  on  the  10th  February, 
1675.  This  theory  is  perhaps  the  loftiest  of  all  his 
speculations ;  and  though,  as  a  physical  generaliza- 
tion, it  stands  on  a  perishable  basis,  and  must  soon 
be  swept  away  in  the  progress  of  science,  it  yet 
bears  the  deepest  impress  of  the  grasp  of  his  pow- 
erful intellect. 

The  principles  upon  which  this  theory  is  founded 
are  the  following : — 

1.  Bodies  that  have  the  greatest  refractive  powers 
reflect  the  greatest  quantity  of  light;  and  at  the 
confines  of  equally  refracting  media  there  is  no  re- 
flection. 1 

2.  The  least  particles  of  almost  all  natural  bodies 
are  in  some  measure  transparent. 

3.  Between  the  particles  of  bodies  are  many  pores 
or  spaces,  either  empty  or  filled  with  media  of  less 
density  than  the  particles. 

4.  The  particles  of  bodies  and  their  pores,  or  the 
spaces  between  the  particles,  have  some  definite 
size. 

Upon  these  principles  Newton  explains  the  origin 
of  transparency,  opacity,  and  colour. 

Transparency^  considers  as  arising  from  the  par- 
ticles and  their  intervals  or  pores  being  too  small  to 
cause  reflection  at  their  common  surfaces,*  so  that 
all  the  light  which  enters  transparent  bodies  passes 
through  them  without  any  portion  of  it  being  turned 
from  its  path  by  reflection.  If  we  could  obtain,  for 
example,  a  film  of  mica  whose  thickness  does  not 
exceed  two-thirds  of  the  millionth  part  of  an  inch, 
all  the  light  which  fell  upon  it  would  pass  through  it 
and  none  would  be  reflected.  If  this  film  was  thei] 

*  Optics,  Book  ii.  Prop.  iv. 


COLOURS   OF   NATURAL   BODIES.  85 

cut  into  fragments,  a  number  of  such  fragments 
would  constitute  a  bundle,  which  would  also  trans- 
mit all  the  light  which  fell  upon  it,  and  be  perfectly 
transparent. 

Opacity  in  bodies  arises,  he  thinks,  from  an  oppo- 
site cause,  viz.  when  the  parts  of  bodies  are  of  such 
a  size  as  to  be  capable  of  reflecting  the  light  which 
falls  upon  them,  in  which  case  the  light  is  "stopped 
or  stifled"  by  the  multitude  of  reflections. 

The  colours  of  natural  bodies  have,  in  the  New- 
tonian hypothesis,  the  same  origin  as  the  colours  of 
thin  plates,  their  transparent  particles,  according  to 
their  several  sizes,  reflecting  rays  of  one  colour,  and 
transmitting  those  of  another.  "For  if  a  thinned 
or  plated  body  which,  being  of  an  uneven  thickness, 
appears  all  over  of  one  uniform  colour,  should  be  slit 
into  threads,  or  broken  into  fragments  of  the  same 
thickness  with  the  plate  or  film,  every  thread  or  frag- 
ment should  keep  its  colour,  and  consequently,  a 
heap  of  such  threads  or  fragments  should  constitute 
a  mass  or  powder  of  the  same  colour  which  the 
plate  exhibited  before  it  was  broken:  and  the  parts 
of  all  natural  bodies  being  like  so  many  fragments 
of  a  plate,  must,  on  the  same  grounds,  exhibit  the 
same  colour." 

Such  is  the  theory  of  the  colours  of  natural 
bodies,  stated  as  clearly  and  briefly  as  we  can.  It 
has  been  very  generally  admitted  by  philosophers, 
both  of  our  own  and  of  other  countries,  and  has  been 
recently  illustrated  and  defended  by  a  French  philoso- 
pher of  distinguished  eminence.  That  this  theory 
affords  the  true  explanation  of  certain  colours,  or, 
to  speak  more  correctly,  that  certain  coloms  in  natu- 
ral bodies  are  the  colours  of  thin  plates,  cannot  be 
doubted;  but  it  will  not  be  difficult  to  show  that  it  is 
quite  inapplicable  to  that  great  class  of  phenomena 
which  may  be  considered  as  representing  the  colours 
of  natural  bodies. 

The  first  objection  to  the  Newtonian  theory  is  the 
H 


86  SIR   ISAAC   NEWTON. 

total  absence  of  all  reflected  light  from  the  particles 
of  transparent  coloured  media,  such  as  coloured 
gems,  coloured  glasses,  and  coloured  fluids.  This 
objection  was  urged  long  ago  by  Mr.  Delaval,  who 
placed  coloured  fluids  on  black  grounds,  and  never 
could  perceive  the  least  trace  of  the  reflected  tints. 
I  have  repeated  the  experiment  with  every  precau- 
tion, and  with  every  variation  that  I  could  think  of, 
and  I  consider  it  as  an  established  fact,  that  in  such 
coloured  bodies  the  complementary  reflected  colour 
cannot  be  rendered  visible.  If  the  fluid,  for  example, 
be  red,  the  green  light  from  which  the  red  has  been 
separated  ought  to  appear  either  directly  by  looking 
into  the  coloured  mass,  or  ought  to  be  recognised 
by  its  influence  in  modifying  the  light  really  re- 
flected; but  as  it  cannot  be  seen,  we  must  conclude 
that  it  has  not  been  reflected,  but  has  been  de- 
stroyed by  some  other  property  of  the  coloured 
body. 

A  similar  objection  may  be  drawn  from  the  disap- 
pearance of  the  transmitted  complementary  colour 
in  the  leaves  of  plants  and  petals  of  flowers.  I  have 
ascertained  from  numerous  experiments,  that  the 
transmitted  colour  is  almost  invariably  the  same 
with  the  reflected  colour,  and  that  the  same  holds 
true  with  the  coloured  juices  expressed  from  them. 
The  complementary  tints  are  never  seen,  and  wher- 
ever there  has  been  any  thing  like  an  approximation 
to  two  tints,  I  have  invariably  found  that  it  arose 
from  there  being  two  different  coloured  juices  exist- 
ing hi  different  sides  of  the  leaf. 

In  the  phenomena  of  the  light  transmitted  by 
coloured  glasses,  there  are  some  peculiarities  which, 
we  think,  demonstrate  that  their  colours  are  not 
those  of  thin  plates.  The  light,  for  example,  trans- 
mitted through  a  particular  kind  of  blue  glass,  has  a 
blue  colour  of  such  a  peculiar  composition  that  there 
is  no  bine  in  any  of  the  orders  of  colours  in  thii 
plates  which  has  any  resemblance  to  it.  It  is  entirely 


COLOURS   OF   NATURAL   BODIES.  87 

destitute  of  the  red  rays  which  form  the  middle  of 
the  red  space  in  the  spectrum;  so  that  the  particles 
on  which  the  colour  depends  must  reflect  the  middle 
red  rays,  and  transmit  those  on  each  side  of  it, — a 
property  which  cannot  be  deduced  from  the  New- 
tonian doctrine. 

The  explanation  of  opacity,  as  arising  from  a 
multitude  of  reflections,  is  liable  to  the  same  ob- 
jection which  we  have  urged  against  the  explana- 
tion of  colour.  In  order  to  appreciate  its  weight, 
we  must  distinguish  opacity  into  two  kinds,  namely, 
the  opacity  of  whiteness  and  the  opacity  of  blackness. 
Those  bodies  which  possess  the  power  of  reflection 
in  the  highest  degree,  such  as  white  metals,  chalk, 
and  plaster  of  Paris,  never  reflect  more  than  one- 
half  of  the  light  which  falls  upon  them.  The  other 
half  of  the  incident  light  is,  according  to  Newton, 
lost  by  a  multitude  of  reflections.  But  how  is  it 
lost  ?  Reflection  merely  changes  the  direction  of  the 
particles  of  light,  so  that  they  must  again  emerge 
from  the  body,  unless  they  are  reflected  into  fixed 
returning  orbits,  which  detain  them  for  ever  in  a 
state  .of  motion  within  the  body.  In  the  case  of 
black  opacity,  such  as  that  of  coal,  which  reflects 
from  its  first  surface  only  J7th  of  the  white  light, 
the  difficulty  is  still  greater,  and  we  cannot  conceive 
how  any  system  of  interior  reflections  could  so 
completely  stifle  f^ths  of  the  whole  incident  light, 
without  some  of  it  returning  to  the  eye  in  a  visible 
form. 

In  determining  the  constitution  of  bodies  that  pro- 
duce transparency  and  blackness,  the  Newtonian 
theory  encounters  a  difficulty  which  its  author  has 
by  no  means  surmounted.  Transparency,  as  we 
have  already  seen,  arises  from  the  "particles  and 
their  interstices  being  too  small  to  cause  reflections 
in  their  common  surfaces,"  that  is,  they  must  be 
"less  than  any  of  those  which  exhibit  colours,"  or 
"less  than  is  requisite  to  reflect  the  white  and  very 


88  «IR   ISAAC   NEWTON. 

faint  blue  of  the  first  order.  But  this  is  the  very  same 
constitution  which  produces  blackness  by  reflection, 
and  in  order  to  explain  the  cause  of  blackness  by 
transmission,  or  black  opacity,  Newton  is  obliged  to 
introduce  a  new  principle. 

".For  the  production  of  black"  says  he,  "the  cor- 
puscles must  be  less  than  any  of  those  which  ex- 
hibit colours.  For  at  all  greater  sizes  there  is  too 
much  light  reflected  to  constitute  this  colour.  But 
if  -they  be  supposed  a  little  less  than  is  requisite  to 
reflect  the  white  and  very  faint  blue  of  the  first  or- 
der, they  will  reflect  so  very  little  light  as  to  appear 
intensely  black,  and  yet  may  perhaps  variously  refract* 
it  to  and  fro  within  themselves  so  long,  until  it  hap- 
pens to  be  stifled  and  lost,  by  which  means  they  will 
appear  black  in  all  positions  of  the  eye,  without  any 
transparency." 

This  very  remarkable  passage  exhibits,  in  a  striking 
manner,  the  perplexity  in  which  our  author  was  in- 
volved by  the  difficulties  of  his  subject.  As  the  par- 
ticles which  produce  blackness  by  reflection  are 
necessarily  so  small  as  to  exclude  the  existence  of 
any  reflective  forces,  he  cannot  ascribe  the  loss  of 
the  intromitted  light,  as  he  does  in  the  case  of  white 
opacity,  to  "  a  multitude  of  reflections ;"  and  there- 
fore he  is  compelled  to  have  recourse  to  refracting 
forces  to  perform  the  same  office.  The  reluctance 
with  which  he  avails  himself  of  this  expedient  is 
well  marked  in  the  mode  of  expression  which  he 
adopts ;  and  I  am  persuaded  that  when  he  wrote  the 
above  passage,  he  felt  the  full  force  of  the  objec- 
tions to  this  hypothesis,  which  cannot  fail  to  pre- 
sent themselves.  As  the  size  of  the  particles  which 
produce  blackness  are  intermediate  between  those 

*  In  the  same  paragraph,  when  speaking  of  black  bodies  becoming 
hot,  and  burning  sooner  than  others,  he  says  that  their  "effect  may  pro- 
ceed partly  from  the  multitude  of  refractions  in  a  little  room,  and  partly 
from  the  easy  commotion  of  so  very  small  corpuscles."— Optics,  Part  iii. 
Prop.  vii.  p.  335. 


COLOURS    OF  NATURAL   BODIES.  89 

which  produce  transparency  and  those  which  pro- 
duce colour,  approaching  closely  to  the  latter,  it  is 
difficult  to  conceive  why  they  should  refract  the  in- 
tromitted  light,  while  the  greater  and  smaller  par- 
ticles, and  even  those  almost  of  the  same  size,  should 
be  destitute  of  that  property  ^  It  is,  besides,  not  easy 
to  understand  how  a  refraction  can  take  place  within 
bodies  which  shall  stifle  all  the  light,  and  prevent  it 
from  emerging.  Nay,  we  may  admit  the  existence 
of  such  refractions,  and  yet  understand  how,  by  a 
compensation  in  their  direction,  the  refracted  rays 
may  all  emerge  from  the  opaque  body. 

The  force  of  these  objections  is  tacitly  recognised 
in  Pemberton's  View  of  Sir  Isaac  Newton's  Philoso- 
phy ;*  and  as  Newton  not  only  read  and  approved  of 
that  work,  but  even  perused  a  great  part  of  it  along 
with  its  author,  we  may  fairly  consider  the  opinion 
there  stated  to  be  his  own. 

"  For  producing  black,  the  particles  ought  to  be 
smaller  than  for  exhibiting  any  of  the  colours,  viz. 
of  a  size  answering  to  the  thickness  of  the  bubble, 
whereby  reflecting  little  or  no  light,  it  appears  colour- 
less; but  yet  they  must  not  be  too  small,  for  that  will 
make  them  transparent  through  deficiency  of  reflec- 
tions in  the  inward  parts  of  the  body,  sufficient  to 
stop  the  light  from  going  through  it ;  but  they  must 
be  of  a  size  bordering  upon  that  disposed  to  reflect 
the  faint  blue  of  the  first  order,  which  affords  an 
evident  reason  why  blacks  usually  partake  a  little 
of  fhat  colour."  In  this  passage  all  idea  of  refrac- 
tion is  abandoned,  and  that  precise  degree  of  size  is 
assumed  for  the  particles  which  leaves  a  small  power 
of  reflection,  which  is  deemed  sufficient  to  prevent 
the  body  from  becoming  transparent;  that  is,  suffi- 
cient to  render  it  opaque  or  black. 

The  last  objection  which  we  shall  state  to  this 
theory  is  one  to  which  we  attach  great  weight,  and, 

*  See  page  354. 

H2 


t)0  SIR  ISAAC  NEWTON. 

as  it  is  founded  on  discoveries  and  views  which  have 
been  published  since  the  time  of  Newton,  we  ven- 
ture to  believe,  that,  had  he  been  aware  of  them,  he 
would  never  have  proposed  the  theory  which  we 
are  considering. 

When  light  falls  upon  a  thin  film  such  as  AEC, 
fig.  9,  p.  80,  so  as  to  produce  the  colours  of  thin 
plates,  it  follows,  from  Sir  Isaac  Newton's  theory 
of  fits,  that  a  portion  of  the  light  is,  as  usual,  re- 
flected at  the  first  surface  AE,*  while  the  light  which 
forms  the  coloured  image  is  that  which  is  reflected 
from  the  second  surface  EC,  so  that  all  the  colours 
of  thin  plates  are  diluted  with  the  white  light  re- 
flected from  the  first  surface.  Now,  in  the  modern 
theory,  which  ascribes  the  colours  of  thin  plates  to 
the  interference  of  the  light  reflected  from  the 
second  surface  EC,  with  the  light  reflected  from  the 
first  surface  AE,  the  resulting  tint  arises  from  the 
combination  of  these  two  pencils,  and  consequently 
there  is  no  wliite  light  reflected  from  the  surface 
AE.  In  like  manner,  when  the  thickness  of  the 
film  is  such  that  the  two  interfering  pencils  com- 
pletely destroy  one  another,  and  produce  black, 
there  is  not  a  ray  of  light  reflected  from  the  first 
surface.  Here,  then,  we  have  a  criterion  for  de- 
ciding between  the  theory  of  fits  and  the  theory  of 
interference ;  for  if  there  is  no  white  light  reflected 
from  the  first  surface  AE,  the  theory  of  fits  must  be 
rejected.  In  a  remarkable  phenomenon  of  black- 
ness arising  from  minute  fibres,  which  I  have  had 
occasion  to  describe,  there  was  no  perceptible  re- 
flection from  the  surface  of  the  fibres  ;f  and  M. 
Fresnel  describes  an  experiment  made  to  deter- 
mine the  same  point,  and  states  the  result  of  it  to 

*  When  Newton  speaks  of  bodies  losing  their  reflecting  power  from 
their  thinness,  he  means  the  reflecting  power  of  their  second  surfaces, 
as  is  evident  from  the  reason  he  assigns.— See  Optics,  Part  iii.  Prop,  xiii, 
p.  257. 

\  Edinburgh  Journal  of  Science,  No  I  p.  108. 


COLOURS    OF  NATURAL   BODIES.  91 

have  been  unequivocally  in  favour  of  the  doctrine 
of  interference. 

In  order  to  apply  this  important  fact,  let  us  take 
a  piece  of  coal,  one  of  the  blackest  and  most  opaque 
of  all  substances,  and  which  does  not  reflect  to  the 
eye  a  single  ray  out  of  those  which  enter  its  sub- 
stance. The  size  of  its  particles  is  so  small,  that 
they  are  incapable  of  reflecting  light.  When  a  num- 
ber of  these  particles  are  placed  together,  so  as  to 
form  a  surface,  and  other  particles  behind  them,  so 
as  to  form  a  solid,  they  will  not  acquire  by  this 
process  the  power  of  reflection ;  and  consequently,  a 
piece  of  coal  so  composed  should  be  destitute  of  the 
property  of  reflecting  light  from  its  first  surface. 
But  this  is  not  the  case, — light  is  abundantly  re- 
flected from  the  first  surface  of  the  coal,  and  conse- 
quently, its  elementary  particles  must  possess  the 
same  power.  Hence  the  blackness  of  coal  must  be 
ascribed  to  some  other  cause  than  to  the  minute- 
ness of  its  transparent  atoms. 

To  transparent  bodies  this  argument  has  a  similar 
application.  As  their  atoms  are  still  less  than  those 
of  black  bodies,  their  inability  to  reflect  light  is  still 
greater,  and  hence  arises  their  transparency.  But 
the  particles  forming  the  surface  of  such  bodies  do 
reflect  light,  and,  therefore,  their  transparency  must 
have  another  origin. 

In  the  case  of  coloured  bodies,  too,  the  particles 
forming  their  surfaces  reflect  white  light  like  those 
of  all  other  bodies,  so  that  these  particles  cannot 
produce  colour  on  the  same  principles  as  those  of 
thin  plates.  In  many  of  those  cases  of  colour  which 
seem  to  depend  upon  the  minuteness  of  the  particles 
of  the  body,  the  reflection  of  white  light  may  never- 
theless be  observed,  but  this  will  be  found  to  arise 
from  a  thin  transparent  film,  behind  which  the  colo- 
rific particles  are  placed. 

Whatever  answer  may  be  given  to  these  objec- 
tions, we  think  it  will  be  admitted  by  those  who 


92  SIR   ISAAC   NEWTON. 

have  studied  the  subject  most  profoundly,  that  a 
satisfactory  theory  of  the  colours  of  natural  bodies 
is  still  a  desideratum  in  science.  How  far  we  may 
be  able  to  approach  to  it  in  the  present  state  of 
optics  the  reader  will  judge  from  the  following 
views. 

Colours  may  be  arranged  into  seven  classes,  each 
of  which  depends  upon  different  principles. 

1.  Transparent  coloured  fluids — transparent  col 
cured  gems — transparent  coloured  glasses — coloured 
powders — and  the  colours  of  the  leaves  and  flowers 
of  plants. 

2.  Oxidations  on  metals — colours  of  Labrador 
feldspar — colours   of   precious   and  hydrophanous 
opal,  and  other  opalescences — the  colours  of  the 
feathers  of  birds,  of  the  wings  of  insects,  and  of  the 
scales  of  fishes. 

3.  Superficial  colours,  as  those  of  mother-of-pearl 
and  striated  surfaces. 

4.  Opalescences  and  colours  in  composite  crystals 
having  double  refraction. 

5.  Colours  from  the  absorption  of  common  and 
polarized  light  by  doubly  refracting  crystals. 

6.  Colours  at  the  surfaces  of  media  of  different 
dispersive  powers. 

7.  Colours  at  the  surface  of  media  in  which  the 
reflecting  forces  extend  to  different  distances,  or  fol- 
low different  laws. 

The  first  two  of  these  classes  are  the  most  im- 
portant. The  Newtonian  theory  appears  to  be 
strictly  applicable  to  the  phenomena  of  the  second 
class ;  but  those  of  the  first  class  cannot,  we  con- 
ceive, be  referred  to  the  same  cause. 

The  rays  of  solar  light  possess  several  remarkable 
physical  properties :  They  heat — they  illuminate 
— they  promote  chymical  combination — they  effect 
chymical  decompositions — they  impart  magnetism 
to  steel — thej  alter  the  colours  of  bodies — thev 


NEW   THEORY   OF   COLOURS.  93 

communicate  to  plants  and  flowers  their  peculiar 
colours,  and  are  in  many  cases  necessary  to  the 
development  of  their  characteristic  qualities.  It  is 
impossible  to  admit  for  a  moment  that  these  varied 
effects  are  produced  by  a  mere  mechanical  action, 
or  that  they  arise  from  the  agitation  of  the  particles 
of  bodies  by  the  vibration  of  the  ether  which  is  con- 
sidered to  be  the  cause  of  light.  Whatever  be  the 
difficulties  which  attach  to  the  theory  which  sup- 
poses light  to  consist  of  material  particles,  we  are 
compelled,  by  its  properties,  to  admit  that  light  acts 
as  if  it  were  material,  and  that  it  enters  into  combi- 
nations with  bodies,  in  order  to  produce  the  effects 
which  we  have  enumerated. 

When  a  beam  of  light  falls  upon  a  body,  and  the 
whole  or  a  part  of  that  which  enters  its  substance 
totally  disappears,  we  are  entitled  to  say,  that  it  is 
detained  by  some  power  exercised  by  the  particles 
of  the  body  over  the  particles  of  light.  When  this 
light  is  said  to  be  lost  by  a  multitude  of  reflections 
or  refractions,  the  statement  is  net  only  hypotheti- 
cal, but  it  is  an  hypothesis  incompatible  with  optical 
principles.  That  the  light  detained  within  bodies 
has  been  stopped  by  the  attractive  force  of  the  par- 
ticles seems  to  be  highly  probable,  and  the  mind 
will  not  feel  any  repugnance  to  admit  that  the  par- 
ticles of  all  bodies,  whether  solid,  fluid,  or  aeriform, 
have  a  specific  affinity  for  the  particles  of  light. 
Considering  light,  therefore,  as  material,  it  is  not 
difficult  to  comprehend  how  it  should,  like  other 
elementary  substances,  enter  into  combination  with 
bodies,  and  produce  many  chymical  and  physical 
effects,  but  particularly  the  phenomena  of  transpa- 
rency, opacity,  and  colour. 

In  transparent  colourless  bodies,  such  as  water 
and  glass,  the  intromitted  light  experiences  a  con- 
siderable loss,  because  a  certain  number  of  its  par- 
ticles are  attracted  and  detained  by  the  atoms  of  the 
water  or  glass,  and  the  light  which  emerges  is 


94  SIR   ISAAC   NEWTON. 

colourless,  because  the  particles  exercise  a  propor- 
tional action  over  all  the  simple  colours  which 
compose  white  light. 

When  the  transparent  body  has  any  decided 
colour,  such  as  those  enumerated  in  Class  L,  then 
the  particles  of  the-  body  have  exercised  a  specific 
attraction  over  those  rays  of  white  light  which  are 
complementary  to  those  which  compose  the  colour 
of  the  transmitted  light.  If  the  transparent  body, 
for  example,  is  red,  then  its  particles  have  detained 
the  green  rays  which  entered  into  the  incident  light, 
or  certain  other  rays,  which  with  the  red  are  neces- 
sary to  compose  white  light.  In  compound  bodies, 
like  some  of  the  artificial  glasses,  the  particles  will 
attract  and  detain  rays  of  light  of  different  colours, 
as  may  be  seen  by  analyzing  the  transmitted  light 
with  a  prism,  which  will  exhibit  a  spectrum  deprived 
of  all  the  rays  which  have  been  detained.  In  black 
bodies  the  particles  exercise  a  powerful  attraction 
over  light,  and  detain  all  the  intromitted  rays. 

When  coloured  bodies  are  opaque,  so  as  to  ex- 
hibit their  colours  principally  by  reflection,  the  light 
which  is  reflected  back  to  the  observer  has  received 
its  colour  from  transmission  through  part  of  the 
thickness  of  the  body,  or,  what  is  the  same  thing, 
the  colour  reflected  to  the  eye  is  complementary  to 
that  which  has  been  detained  by  the  particles  of  the 
body  while  the  light  is  passing  and  repassing 
through  a  thickness  terminated  by  the  reflecting 
surfaces ;  and  as  only  a  part  of  this  light  is  reflected, 
as  in  the  case  of  leaves  and  flowers,  the  transmitted 
light  must  have  the  same  colour  as  the  reflected 
light. 

When  coloured  bodies  exhibit  two  different  colours 
complementary  to  each  other,  the  one  seen  by  re- 
flection and  the  other  by  transmission,  it  is  then 
highly  probable  that  the  colours  are  those  of  thin 
plates,  though  there  are  still  other  optical  principles 
to  which  they  may  be  referred.  As  the  particles  of 


NEW   THEORY   OF    COLOURS.  95 

|  bodies,  and  the  medium  which  unites  them,  or.  as 
the  different  atoms  of  a  compound  body  may  have 
different  dispersive  powers,  while  they  exercise  the 
same  refractive  force  over  a  particular  part  of  the 
spectrum,  the  rays  for  which  this  compensation 
takes  place  will  be  transmitted,  while  part  of  the 
complementary  light  is  reflected.*  Or  in  cases 
where  the  refractive  and  dispersive  powers  are  the 
same,  the  reflective  forces  of  the  particles  may  vary 
according  to  a  different  law,  so  that  at  the  separat- 
ing surfaces  either  white  or  coloured  light  may  be 
reflected.f 

In  those  cases  of  colour  where  the  reflected  and 
the  transmitted  tints  are  not  complementary,  as  in 
leaf-gold,  where  the  former  is  yellow  and  the  latter 
green; — in  leaf -silver,  where  they  are  white  and  blue, 
and  in  certahTpieees  of  fir-wood,  where  the  reflected 
light  is  whitish  yellow,  and  the  transmitted  light  a 
brilliant  homogeneous  red,  we  may  explain  the  sepa- 
ration of  the  colours  either  by  the  principles  we 
have  already  laid  down  or  by  the  doctrine  of 'thin 
plates.  On  the  first  principle,  the  colour  of  the  re- 
flected light,  which  is  supposed  to  be  the  same  as 
that  of  the  transmitted  light,  will  be  modified  by  the 
law  according  to  which  the  particles  of  the  body 
attract  different  rays  out  of  the  beam  of  white  light. 
In  pitch,  for  example,  the  blue  rays  are  first  ab- 
sorbed, so  that  at  small  thicknesses  the  transmitted 
light  is  a  fine  yellow,  while,  by  the  action  of  a 
greater  thickness,  the  yellow  itself  is  absorbed,  and 
the  transmitted  light  is  a  bright  homogeneous  red. 
Now  in  leaf-gold  the  transmitted  colour  of  thinner 
films  than  we  can  obtain  may  be  yellow,  and,  con- 
sequently, the  light  reflected  from  the  first  strata  of 
interrupting  faces  will  be  yellow,  and  will  determine 
the  predominant  tint  of  the  reflected  light.  On  the 
Newtonian  doctrine,  Mr.  Herschel  has  explained  it 

*  See  the  Phil.  Trans.  1829,  Part  I.  p.  189. 


96 


SIR    ISAAC    NEWTON. 


by  saying",  "  that  the  transmitted  rays  have  traversed 
the  whole  thickness  of  the  medium,  and  therefore 
undergo  many  more  times  the  action  of  its  atoms 
than  those  reflected,  especially  those  near  the  first 
surface  to  which  the  brighter  part  of  the  reflected 
colour  is  due." 

The  phenomena  of  the  absorption  of  common 
and  polarized  light,  which  I  have  described  in  an- 
other place,*  throw  much  light  on  the  subject  of 
coloured  bodies.  The  relation  of  the  absorbent  ac 
tion  to  the  axes  of  double  refraction,  and,  conse- 
quently, to  the  poles  of  the  molecules  of  the  crystal, 
shows  how  the  particles  of  light  attracted  by  the 
molecules  of  the  body  will  vary,  both  in  their  nature 
and  number,  according  to  the  direction  in  which 
they  approach  the  molecules ;  and  explains  how  the 
colour  of  a  body  may  be  changed,  either  tempora- 
rily or  permanently,  by  heat,  according  as  it  pro- 
duces a  temporary  or  a  permanent  change  in  the 
relative  position  of  the  molecules.  This  is  not  the 
place  to  enlarge  on  this  subject ;  but  we  may  be 
permitted  to  apply  the  idea  to  the  curious  experi- 
ment of  Thenard  on  phosphorus.  When  this  sub- 
stance is  rendered  pure  by  repeated  distillation,  it 
is  transparent,  and  transmits  yellow  light ;  but  when 
it  is  thrown  in  a  melted  state  into  cold  water,  it 
becomes  jet  black.  When  again  melted,  it  resumes 
its  original  colour  and  transparency.  According  to 
the  Newtonian  theory,  we  must  suppose  that  the 
atoms  of  the  phosphorus  have  been  diminished  in 
size  by  sudden  cooling, — an  effect  which  it  is  not 
easy  to  comprehend;  but,  according  to  the  pre- 
ceding views,  we  may  suppose  that  the  atoms  of 
the  phosphorus  have  been  forced  by  sudden  cooling 
into  relative  positions  quite  different  from  those 
which  they  take  when  they  slowly  assume  the  solid 
state,  and  their  poles  of  maximum  attraction,  in 

*  Phil.  Trans.  1819,  p.  11. 


NEW  THEORY  OF   COLOURS.  9? 

place  of  being  turned  to  one  another,  are  turned  in 
{different  directions,  and  then  allowed  to  exercise 
their  full  action  in  attracting  the  intromitted  light, 
and  detaining  it  wholly  within  the  body.* 

Before  concluding  this  chapter,  there  is  one  topic 
peculiarly  deserving  our  notice,  namely,  the  change 
of  colour  produced  in  bodies  by  continued  exposure 
to  light.  The  general  effect  of  light  is  to  diminish 
or  dilute  the  colours  of  bodies,  and  in  many  cases 
to  deprive  them  entirely  of  their  colour.  Now,  it 
is  not  easy  to  understand  how  repeated  undulations 
propagated  through  a  body  could  diminish  the  size 
of  its  particles,  or  how  the  same  effect  could  be 
produced  by  a  multitude  of  reflections  from  particle 
to  particle.  But  if  light  is  attracted  by  the  particles 
of  bodies,  and  combines  with  them,  it  is  easy  to 
conceive  that,  when  the  molecules  of  a  body  have 
combined  with  a  great  number  of  particles  of  a 
green  colour,  for  example,  their  power  of  combina- 
tion with  others  will  be  diminished,  and,  conse- 
quently, the  number  of  particles  of  any  colour 
(absorbed  or  detained  must  diminish  with  the  time 
that  the  body  has  been  exposed  to  light ;  that  is, 
[these  particles  must  enter  into  the  transmitted  and 
((reflected  pencils,  and  diminish  the  intensity  of  their 
colour.  If  the  body,  for  example,  absorbs  red  light, 
and  transmits  and  reflects  green,  then  if  the  quan- 
tity of  absorbed  red  light  is  diminished,  it  will  enter 
into  the  reflected  and  transmitted  pencils,  and,  form- 
ing white  light  by  its  mixture  with  a  portion  of  the 
green  rays,  will  actually  dilute  them  in  the  same 
manner  as  if  a  portion  of  white  light  had  been 
added.f 

*  If  this  view  of  the  matter  be  just,  we  should  expect  that  the  specific 
gravity  of  the  black  would  exceed  that  of  the  yellow  phosphorus. 

t  Since  the  two  preceding  chapters  were  written,  I  have  had  occasion 
to  confirm  and  extend  the  views  which  they  contain  by  many  new  ex- 
periments. 


08  SIR  ISAAC  NEWTON. 


CHAPTER  VIII. 

Newton's  Discoveries  respecting  the  Inflection  or  Diffraction  of  Light 
— Previous  Discoveries  of  Grimaldi  and  Dr.  Hooke — Labours  of  sue* 
ceeding  Philosophers— Law  of  Interference  of  Dr.  Young— FresneVt 
Discoveries — New  Theory  of  Inflection  on  the  Hypothesis  of  the  Ma- 
teriality of  Light. 


ALTHOUGH  the  discoveries  of  Newton  respectin^ 
the  Inflection  of  Light  were  first  published  in  hisl 
Optics  in  1704,  yet  there  is  reason  to  think  that 
they  were  made  at  a  much  earlier  period.  Sir  Isaac,; 
indeed,  informs  us,  in  his  preface  to  that  great  worfy 
that  the  third  book,  which  contains  these  discove- 
ries, "  was  put  together  out  of  scattered  papers  ;'* 
and  he  adds  at  the  end  of  his  observations,  that  "  he 
designed  to  repeat  most  of  them  with  more  care  and 
exactness,  and  to  make  some  new  ones  for  determin- 
ing the  manner  how  the  rays  of  light  are  bent  in  their 
passage  by  bodies,  for  making  the  fringes  of  colours 
with  the  dark  lines  between  them.  But  I  was  then 
interrupted,  and  cannot  now  think  of  taking  these 
things  into  consideration."  On  the  18th  March,  1674, 
Dr.  Hooke  had  read  a  valuable  memoir  on  the  phe- 
nomena of  diffraction ;  and,  as  Sir  Isaac  makes  no 
allusion  whatever  to  this  work,  it  is  the  more  proba- 
ble that  his  "  scattered  papers"  had  been  written 
previous  to  the  communication  of  Dr.  Hooke's  ex- 
periments. 

The  phenomena  of  the  inflection  of  light  were  first 
discovered  by  Francis  Maria  Grimaldi,  a  learned 
Jesuit,  who  has  described  them  in  a  posthumous 
work  published  in  1665,  two  years  after  his  death.* 

Having  admitted  a  be  am  of  the  sun's  light  through 

*  Pkysieo-Mathesis  de  Lumine  coloribus  et  iride  aliisyue^annexit, 
Bonon  1666. 


INFLECTION   OF  LIGHT.  3$ 

a  small  pin-hole  in  a  piece  of  lead  or  card  into  a 
dark  chamber,  he  found  that  the  light  diverged  from 
this  aperture  in  the  form  of  a  cone,  and  that  the 
shadows  of  all  bodies  placed  in  this  light  were  not 
only  larger  than  might  have  been  expected,  but  were 
surrounded  with  three  coloured  fringes,  the  nearest 
the  widest,  and  the  most  remote  the  narrowest. 
[n  strong  light  he  discovered  analogous  fringes 
within  the  shadows  of  bodies,  which  increased  in 
number  with  the  breadth  of  the  body,  and  became 
more  distinct  when  the  shadow  was  received  obliquely 
and  at  a  greater  distance.  When  two  small  aper- 
;ures  or  pin-holes  were  placed  so  near  each  other 
that  the  cones  of  light  formed  by  each  of  them 
ntersected  one  another,  Grimaldi  observed,  that  a 
spot  common  to  the  circumference  of  each,  or,  which 
s  the  same  thing,  illuminated  by  rays  from  each 
eone,  was  darker  than  the  same  spot  when  illumi- 
nated by  either  of  the  cones  separately ;  and  he  an- 
nounces this  remarkable  fact  in  the  following  para- 
doxical proposition,  "  that  a  body  actually  illuminated^ 
may  become  more  dark  by  adding  a  light  to  that  which  \ 
t  already  receives" 

Without  knowing  what  had  been  done  by  the 
kalian  philosopher,  our  countryman,  Dr.  Robert 
looke,  had  been  diligently  occupied  with  the  same 
subject.  In  4§7&.  he  communicated  his  first  obser- 
vations to  the  Royal  Society,  and  he  then  spoke  of 
lis  paper  as  "  containing  the  discovery  of  a  new 
>roperty  of  light  not  mentioned  by  any  optical  wri- 
;ers  before  him."  In  his  paper  of  1674,  already 
mentioned,  and  which  is  no  doubt  the  one  to~  which 
he  alludes,  he  has  not  only  described  the  leading 
phenomena  of  the  inflection,  or  the  deflection  of 
light,  as  he  calls  it,  but  he  has. distinctly  announced 
the  doctrine  of  interference,  which  has  performed  so 
great  a  part  in  the  subsequent  history  of  optics.* 

This  doctrme  is  thus  announced.    1.  That  the  same  rays  of  light 
upon  the  same  point  of  an  object  will  turn  into  all  sorts  of  colour* 


100 


SIR  ISAAC   NEWTON. 


Such  was-  the  state  of  the  subject  when  Newton 
directed  to  it  his  powers  of  acute  and  accurate  ob- 
servation. His  attention  was  turned  only  to  the 
enlargement  of  the  shadow,  and  to  the  three  fringes 
which  surrounded  it ;  and  he  begins  his  observations 
by  ascribing  the  discovery  of  these  facts  to  Gri- 
maldi.  After  taking  exact  measures  of  the  diameter 
of  the  shadow  of  a  human  hair,  and  of  the  breadth 
of  the  fringes  at  different  distances  behind  it,  he 
discovered  the  remarkable  fact  that  these  diame- 
ters and  breadths  were  not  proportional  to  the  dis- 
tances from  the  hair  at  which  they  were  measured. 
In  order  to  explain  these  phenomena,  Newton  sup- 
posed that  the  rays  which  passed  by  the  edge  of  the 
hair  are  deflected  or  turned  aside  from  it,  as  if  by  a 
repulsive  force,  the  nearest  rays  suffering  the  great- 
est, and  those  more  remote  a  less  degree  of  deflec- 
tion. 

Fig.  10. 


by  the  various  inclination  of  the  object.  2.  That  colours  begin  to  appear 
when  two  pulses  of  light  are  blended  so  well  and  so  near  together  that 
the  sense  takes  them  for  one. 


INFLECTION   OF   LIGHT.  tfl 

Thus,  if  X,  fig.  10,  represents  a  section  of  the 
hair,  and  AB,  CD,  EF,  GH,  &c.  rays  passing  at  dif- 
ferent distances  from  X,  the  ray  AB  will  be  more 
deflected  than  CD,  and  will  cross  it  at  m,  the  ray 
CD  will  for  the  same  reason  cross  EF  at  n,  and 
EF  will  cross  GH  at  o.  Hence  the  curve  or  caustic 
formed  by  the  intersections  m,  n,  o,  &c.  will  be  con- 
vex outward,  its  curvature  diminishing  as  it  recedes 
from  the  vertex.  As  none  of  the  passing  light  can 
possibly  enter  within  this  curve,  it  will  form  the 
boundary  of  the  shadow  of  X. 

The  explanation  given  by  Sir  Isaac  of  the  coloured 
fringes  is  less  precise,  and  can  be  inferred  only  from 
the  two  following  queries. 

1.  "Do  not  the  rays  which  differ  in  refrangibility 
differ  also  in  flexibility,  and  are  they  not,  by  these 
different  inflections  separated  from  one  another,  so 
as  after  separation  to  make  the  colours  in  the  three 
fringes  above  described  1    And  after  what  manner 
are  they  inflected  to  make  those  fringes  1 

2.  "  Are  not  *the  rays  of  light  in  passing  by  the 
edges  and  sides  of  bodies  bent  several  times  back- 
wards and  forwards  with  a  motion  like  that  of  an 
eel  ?    And  do  not  the  three  fringes  of  light  above 
mentioned  arise  from  three  such  bendings  ?" 

The  idea  thus  indistinctly  thrown  out  in  the  pre- 
ceding queries  has  been  ingeniously  interpreted  by 
Mr.  Herschel  in  the  manner  represented  in  fig.  11, 
where  SS  are  two  rays  passing  by  the  edge  of  the 
body  MN.  These  rays  are  supposed  to  undergo 
several  bendings,  as  at  a,  b,  c,  and  the  particles  of 
light  are  thrown  off  at  one  or  other  of  the  points 
of  contrary  flexure,  according  to  the  state  of  their 
fits  or  other  circumstances.  Those  that  are  thrown 
outwards  in  the  direction  «A,  &B,  cC,  dD,  will 
produce  as  many  caustics  by  their  intersections  as 
there  are  deflected  rays;  and  each  caustic,  when  re- 
ceived on  a  screen  at  a  distance,  will  depict  on  it 
the  brightest  part  or  maximum  of  a  fringe. 
12 


102  SIR  ISAAC  NEWTON. 

Fig.  11.  S    S 


In  this  unsatisfactory  state  was  the  subject  of  the 
inflection  of  light  left  by  Sir  Isaac.  His  inquiries 
were  interrupted,  and  never  again  renewed;  and 
though  he  himself  found  that  the  phenomena  were 
the  same,  "  whether  the  hair  was  encompassed  with 
air  or  with  any  other  pellucid  substance,"  yet  this 
important  result  does  not  seem  to  have  shaken  his 
conviction,  that  the  phenomena  had  their  origin  in 
the  action  of  bodies  upon  light. 

During  two  sets  of  experiments  which  I  made  on 
the  inflection  of  light,  the  first  in  1798,  and  the 
second  in  1812  and  1813, 1  was  desirous  of  examin- 
ing the  influence  of  density  and  refractive  power 
over  the  fringes  produced  by  inflection.  T  com- 


DR.  YOUNG'S  LAW  OF  INTERFERENCE.          103 

pared  the  fringes  formed  by  gold-leaf  with  those 
formed  by  masses  of  gold, — and  those  produced  by 
films  which  gave  the  colours  of  thin  plates  with 
those  formed  by  masses  of  the  same  substance.  I 
examined  the  influence  of  platinum,  diamond,  and 
cork  in  inflecting  light,  the  effect  of  non-reflecting 
grooves  and  spaces  in  polished  metals,  and  of  cylin- 
ders of  glass  immersed  in  a  mixture  of  oil  of  cassia 
and  oil  of  olives  of  the  same  refractive  power;  and, 
as  the  fringes  had  the  same  magnitude  and  charac- 
ter under  all  these  circumstances,  I  concluded  that 
they  were  not  produced  by  any  force  inherent  in 
the  bodies  themselves,  but  arose  from  a  property 
of  the  light  itself,  which  always  showed  itself  when 
light  was  stopped  in  its  progress. 

Dr.  Thomas  Young,  who  had  supported  with  great 
ingenuity  and  force  of  argument  the  undulatory 
theory  of  light,  as  maintained  by  Hooke  and  Huy- 
gens,  was  the  first  who  gave  a  plausible  explana- 
tion of  the  inflection  of  light.  By  interposing  a 
small  screen  at  B,  fig.  10,  and  intercepting  the 
rays  that  passed  near  the  hair  X,  he  was  surprised 
to  find  that  all  the  fringes  within  the  shadow  disap- 
peared. The  same  effect  took  place  when  the  screen 
intercepted  the  rays  on  the  other  side  ;  and  hence 
he  concluded,  that  the  rays  on  each  side  of  the  hair 
were  necessary  to  the  production  of  the  inner  fringes, 
and  that  the  fringes  were  produced  by  the  inter" 
ference  of  the  rays  that  passed  on  one  side  of  the 
hair  with  those  that  passed  on  the  other  side.  In 
order  to  account  for  the  coloured  fringes  without  the 
shadow,  Dr.  Young  conceived  that  the  rays  which 
pass  near  the  edge  of  the  hair  interfere  with  others, 
which  he  supposes  may  be  reflected  after  falling 
very  obliquely  upon  its  edge, — a  supposition  which, 
if  correct,  would  certainly  produce  fringes  very 
similar  to  those  actually  observed. 

In  pursuing  these  researches  so  successfully  begun 
by  Dr.  Young,  M.  Fresnel  had  the  good  fortune  to 


104  SIR    ISAAC   NEWTON. 

explain  all  the  phenomena  of  inflection  by  means  of 
the  undulatory  doctrine  combined  with  the  principle 
of  interference.  In  place  of  transmitting  the  light 
through  a  small  aperture,  he  caused  it  to  diverge 
from  the  focus  of  a  deep  convex  lens,  and  instead 
of  receiving  the  shadow  and  its  fringes  upon  a 
smooth  white  surface,  as  was  done  by  Newton,  he 
viewed  them  directly  with  his  eye  through  a  lens 
placed  behind  the  shadow ;  and  by  means  of  a  mi- 
croscope he  was  able  to  measure  the  dimensions  of 
the  fringes  with  the  greatest  exactness.  By  this 
mode  of  observation  he  made  the  remarkable  dis- 
covery, that  the  inflection  of  the  light  depended  on 
the  distance  of  the  inflecting  body  from  the  aperture  or 
from  the  focus  of  divergence  ;*  the  fringes  being  ob- 
served to  dilate  as  the  body  approached  that  focus, 
and  to  contract  as  it  receded  from  it,  their  relative 
distances  from  each  other,  and  from  the  margin  of 
the  shadow  continuing  invariable.  In  attempting  to 
account  for  the  formation  of  the  exterior  fringes,  M. 
Fresnel  found  it  necessary  to  reject  the  supposition 
of  Dr.  Young,  that  they  were  owing  to  light  re- 
flected from  the  edge  of  the  body.  He  not  only 
ascertained  that  the  real  place  of  the  fringe  was  the 
•nnjth  of  a  millimetre  different  from  what  it  should 
be  on  that  supposition,  but  he  found  that  the  fringes 
preserved  the  same  intensity  of  light,  whether  the 
inflecting  body  had  a  round  or  a  sharp  edge,  and 
even  when  the  edge  was  such  as  not  to  afford  suffi- 
cient light  for  their  production.  From  this  difficulty 
the  undulatory  theory  speedily  released  him,  and  he 
was  led  by  its  indications  to  consider  the  exterior 
fringes,  as  produced  by  an  infinite  number  of  ele- 
mentary waves  of  light  emanating  from  a  primitive 
wave  when  partly  interrupted  by  an  opaque  body. 
The  various  phenomena  of  inflection,  which  had 

*  This  effect  is  so  great,  that  at  the  distance  of  four  inches  from  the 
point  of  divergence,  the  angular  inflexion  of  the  red  rays  of  the  first  fringe 
is  12'  6",  while  at  the  distance  of  about  twenty  feet,  it  is  onlv  3'  55" 


NEW   THEORY    OF    INFLECTION.  105 

so  long  resisted  every  effort  to  generalize  them, 
having  thus  received  so  beautiful  and  satisfactory  an 
explanation  from  the  undulatory  doctrine,  they  must 
of  course  be  regarded  as  affording  to  that  doctrine 
the  most  powerful  support,  while  the  Newtonian 
hypothesis  of  the  materiality  of  light  is  proportion- 
ally thrown  into  the  shade.  It  is  impossible,  indeed, 
even  for  national  partiality  to  consider  the  views  of 
Newton  as  furnishing  any  explanation  of  the  facts 
discovered  by  Fresnel ;  and,  as  no  attempt  has  been 
made  by  the  small  though  able  phalanx  of  his  dis- 
ciples to  stay  the  decision  with  which,  on  this  count 
at  least,  the  doctrine  of  emission  has  been  threat- 
ened, we  shall  venture  to  suggest  some  principles 
by  which  the  refractory  phenomena  may  perhaps 
be  yet  brought  within  the  pale  of  the  Newtonian 
theory.  _ 

That  the  particles  of  light,  like  those  of  heat,  ^ 
are  endowed  with  a  repulsive  force  which  prevents 
them  from  accumulating  when  in  a  state  of  conden- 
sation, or  when  they  are  detained  by  the  absorptive 
action  of  opaque  bodies,  will  be  readily  admitted. 
By  this  power  a  beam  of  light  radiating  from  a 
luminous  point  has,  in  every  azimuth,  the  same  de- 

I  gree  of  intensity  at  the  same  distance  from  its  centre 
of  divergence ;  but  if  we  intercept  a  portion  of  such 

!  a  beam  by  an  opaque  body,  the  repulsive  force  of  the 
light  which  formerly  occupied  its  shadow  is  with- 
drawn, and  consequently  the  rays  which  pass  near 
the  body  will  be  repelled  into  the  shadow,  and  will 
form,  by  their  interference  with  those  similarly  re- 
pelled on  the  other  side,  the  interior  fringes,  which 
are  parallel  to  the  edges  of  the  body.  The  rays 
which  pass  at  a  greater  distance  will  in  like  manner 
be  bent  towards  the  body,  but  with  less  force,  and, 
interfering  with  those  rays  which  retain  their  primi- 
tive direction,  from  the  state  of  their  fits  or  the 
position  of  their  poles,  they  will  form  the  exterior 
fringes.  When  the  inflecting  body  is  placed  near 


1€0  SIR   ISAAC   NEWTON. 

the  point  of  divergence,  the  greater  proximity  of 
the  rays  will  produce  a  greater  repulsive  force,  and 
consequently  a  greater  inflection  of  the  passing 
light ;  while  the  removal  of  the  body  from  the  point 
of  divergence  will  be  accompanied  with  an  increased 
distance  of  the  particles,  an  inferior  repulsive  force, 
and  a  feebler  inflection.  As  the  phenomena  of  in- 
flection, considered  under  this  aspect,  arise  from  a 
property  of  the  light  itself,  it  follows  that  they  will 
remain  invariable,  whatever  be  the  nature  or  den- 
sity of  the  body,  or  the  form  of  the  edge  which 
acts  upon  the  passing  rays. 


CHAPTER  IX. 

Miscellaneous  Optical  Researches  of  Newton— ffis  Experiments  on 
Refraction— His  Conjecture  respecting  the  Inflammability  of  the 
Diamond — His  Law  of  Double  Refraction — His  Observations  on  the 
Polarization  of  Light—Newton's  Theory  of  Light— His  "Optics* 

BEFORE  concluding  our  account  of  Newton's  op- 
tical discoveries,  it  is  necessary  to  notice  some  of 
his  minor  researches,  which,  though  of  inferior  im- 
portance in  the  science  of  light,  have  either  exer- 
cised an  influence  over  the  progress  of  discovery, 
or  been  associated  with  the  history  of  other  branches 
of  knowledge. 

One  of  the  most  curious  of  these  inquiries  related 
to  the  connexion  between  the  refractive  powers  and 
the  chymical  composition  of  bodies.  Having  meas- 
ured the  refractive  powers  and  the  densities  of  twenty- 
two  substances,  he  found  that  the  forces  which 
reflect  and  refract  light  are  very  nearly  proportional 
to  the  densities  of  the  same  bodies.  In^  this  law, 
however,  he  noticed  a  remarkable  exception  in  the 
case  of  unctuous  and  sulphureous  bodies,  such  as 
camphire,  olive  oil,  linseed  oil,  spirit  of  turpentine, 


DOUBLE   REFRACTION   OF   LIGHT.  107 

and  diamond,  which  have  their  refractive  powers 
two  or  three  times  greater  in  respect  of  their  densi- 
ties than  the  other  substances  in  the  table,  while 
among  themselves  their  refractive  powers  are  pro- 
portional to  their  densities,  without  any  considerable 
variation.  Hence  he  concluded  that  diamond  "  is 
an  unctuous  substance  coagulated," — a  sagacious 
prediction,  which  has  been  verified  in  the  discoveries 
of  modern  chymistry.  The  connexion  between  a 
high  degree  of  inflammability  and  a  great  refracting 
force  has  been  still  more  strongly  established  by  the 
high  refractive  power  which  I  detected  in  phospho- 
rus, and  which  was  discovered  in  hydrogen  by  MM. 
Biot  and  Arago. 

There  is  no  part  of  the  optical  labours  of  Newton 
which  is  less  satisfactory  than  that  which  relates  to 
the  double  refraction  of  light.  In  1690,  Huygens, 
published  his  admirable  treatise  on  light,  in  which 
he  has  given  the  law  of  double  refraction  in  calca- 
reous spar,  as  deduced  from  his  theory  of  light,  and 
as  confirmed  by  direct  experiment.  Viewing  it 
probably  as  a  theoretical  deduction,  Newton  seems 
to  have  regarded  it  as  incorrect,  and  though  he  has 
given  Huygens  the  credit  of  describing  the  phe- 
nomena more  exactly  than  Bartholinus,  yet,  without 
assigning  any  reason,  he  rejected  the  law  of  the 
Dutch  philosopher,  and  substituted  another  in  its 
place.  These  observations  of  our  author  form  the 
subject  of  the  twenty-fifth  and  twenty-sixth  queries  at 
the  end  of  his  Optics,  which  was  published  fourteen 
years  after  the  appearance  of  Huygens's  work.  The 
law  adopted  by  Newton  is  not  accompanied  with  any 
of  the  experiments  from  which  it  was  deduced ;  and 
though  he  has  given  it  without  expressing  any  doubt 
of  its  accuracy,  it  is,  nevertheless,  entirely  incom- 
patible with  observation,  and  has  been  rejected  by 
all  succeeding  philosophers. 

In  his  speculations  respecting  the  successive  dis- 
appearance and  reappearance  of  two  of  the  four 


108  SIR  ISAAC  NEWTON. 

images  which  are  formed  when  a  luminous  objecl 
is  viewed  through  two  rhombs  of  calcareous  spar, 
one  of  which  is  made  to  revolve  upon  the  other. 
Newton  has  been  more  successful.  He  concluded 
from  these  phenomena  that  every  ray  of  light  has 
two  opposite  sides  originally  endued  with  the  prop- 
erty on  which  the  unusual  refraction  depends,  and 
other  two  opposite  sides  not  endued  with  that  prop- 
erty; and  he  suggested  it  as  a  subject  for  future 
inquiry,  whether  there  are  not  more  properties  of 
light  by  which  the  sides  of  the  rays  differ,  and  are 
distinguished  from  one  another.  This  is  the  first 
occasion  on  which  the  idea  of  a  polarity  in  the  rays 
of  light  has  been  suggested.* 

From  the  various  optical  inquiries  in  which  New- 
ton was  engaged,  he  was  strongly  impressed  with 
the  belief  that  light  consists  of  small  material  par- 
ticles emitted  from  shining  substances,  and  that 
these  particles  could  be  again  recombined  into  solid 
matter,  so  that  "  gross  bodies  and  light  were  con- 
vertible into  one  another."  He  conceived  also  that 
the  particles  of  solid  bodies  and  of  light  exerted  a 
mutual  action  upon  each  other,  the  former  being 
agitated  and  heated  by  the  latter,  and  the  latter 
being  attracted  and  repelled  by  the  former,*  with 
forces  depending  on  the  inertia  of  the  luminous  par- 
ticles. These  forces  he  regarded  as  insensible  at 
all  measurable  distances,  and  he  conceived  that  the 
distances  between  the  particles  of  bodies  were  very 
small  when  compared  with  the  extent  of  their  sphere 
of  attraction  and  repulsion. 

With  the  exception  of  Hooke,  Huygens,  and 
Euler,  almost  all  the  contemporaries  and  successors 
of  Newton  maintained  the  doctrine  of  the  mate- 
riality of  light.  It  was  first  successfully  assailed  by 
Dr.  Thomas  Young,  and  since  that  time  it  has  been 
shaken  to  its  foundation  by  those  great  discoveries 

': 

*  See  the  twenty-ninth  query  at  the  end  of  his  Optics,  where  the  sides 
of  a  ray  are  compared  with  the  poles  of  a  magnet. 


OPTICS.  109 

which  have  illustrated  the  commencement  of  the 
present  century.  The  undulatory  theory,  which  has 
thus  triumphed  in  its  turn,  is  still  subject  to  grave 
difficulties,  and  we  fear  another  century  must  elapse 
before  a  final  decision  can  be  pronounced  on  this 
Jong-agitated  question. 

The  most  important  of  the  optical  discoveries  of 
Newton,  of  which  we  have  given  a  general  history, 
were  communicated  to  the  Royal  Society  in  de- 
tached papers ;  but  the  disputes  in  which  they  had 
involved  their  author  made  him  hesitate  about  the 
publication  of  his  other  discoveries.  Although  he 
had  drawn  up  a  connected  view  of  his  labours  under 
the  title  of  "  Opticks,  or  a  Treatise  on  the  Reflex- 
ions, Refractions,  Inflexions,  and  Colours  of  Light," 
yet  he  resolved  not  to  publish  this  work  during  the 
life  of  Hooke,  by  whose  rival  jealousy  his  tranquillity 
had  been  so  frequently  interrupted.  Hooke,  how- 
ever, died  in  1702,  and  the  Optics  of  Newton  ap- 
peared in  English  in  1704.  Dr.  Samuel  Clark  pro- 
posed a  Latin  edition  of  it,  which  appeared  in  1706, 
and  he  was  generously  presented  by  Sir  Isaac  with 
500/.  (or  100/.  for  each  of  his  five  children),  as  a 
token  of  the  approbation  and  gratitude  of  the  author. 
Both  the  English  and  the  Latin  editions  have  been 
frequently  reprinted  both  in  England  and  on  the 
Continent,*  and  there  perhaps  never  was  a  work  of 
profound  science  so  widely  circulated 

*  Tfce  English  edition  was  reprinted  at  London  in  1714,  1721,  and 
1730,  and  the  Latin  one  at  London  in  1706, 1719, 1721, 1728,  at  Lausanne 
in  1740,  aud  at  Padua  in  1773. 


110  SIR  ISAAC   NEWTON. 


CHAPTER  X. 

Astronomical  Discoveries  of  Newton— Necessity  of  combined  Exertion 
to  the  Completion  of  great  Discoveries — Sketch  of  the  History  of  As- 
tronomy previous  to  the  Time  of  Newton — Copernicus,  1473-1543 — 
Tycho  Brake,  1546-1601— Kepler,  1571-1631— Galileo,  1564-1642. 

FROM  the  optical  labours  of  Newton  we  now  pro- 
ceed to  the  history  of  his  astronomical  discoveries 
— those  transcendent  deductions  of  human  reason 
by  which  he  has  secured  to  himself  an  immortal 
name,  and  vindicated  the  intellectual  dignity  of  his 
species.  Pre-eminent  as  his  triumphs  have  been,  it 
would  be  unjust  to  affirm  that  they  were  achieved 
by  his  single  arm.  The  torch  of  many  a  preceding 
age  had  thrown  its  light  into  the  strongholds  of 
the  material  universe,  and  the  grasp  of  many  a  pow- 
erful hand  had  pulled  down  the  most  impregnable  of 
its  defences.  An  alliance,  indeed,  of  many  kindred 
spirits  had  been  long  struggling  in  this  great  cause, 
and  Newton  was  but  the  leader  of  their  mighty 
phalanx, — the  director  of  their  combined  genius, — 
the  general  who  won  the  victory,  and  therefore 
wears  its  laurels. 

The  history  of  science  presents  us  with  no  ex- 
ample of  an  individual  mind  throwing  itself  far  in 
advance  of  its  contemporaries.  It  is  only  in  the 
career  of  crime  and  ambition  that  reckless  man 
takes  the  start  of  his  species,  and,  uncurbed  by 
moral  and  religious  restraint,  erects  an  unholy  dy- 
nasty upon  the  ruins  of  ancient  and  venerable  insti- 
tutions. The  achievements  of  intellectual  power, 
though  often  begun  by  one  mind  and  completed  by 
another,  have  ever  been  the  results  of  combined  ex- 
ertions. Slow  in  their  growth,  they  gradually  ap- 
proximate to  a  more  perfect  condition : — the  variety 


ASTRONOMICAL   DISCOVERIES.  Ill 

i»  the  phenomena  of  nature  call  forth  a  variety  of 
intellectual  gifts  ; — the  powers  of  analysis  and  com- 
bination are  applied  to  the  humbler  labours  of  obser 
vation  and  experiment,  and  in  the  ordeal  of  rival 
inquiry  truth  is  finally  purified  from  error.  How 
different  is  it  with  those  systems  which  the  imagi- 
nation rears, — those  theories  of  wild  import  which 
are  directed  against  the  consciences  and  hopes  of 
man.  The  fatal  upas-tree  distils  its  poison  in  the 
spring  as  well  as  the  autumn  of  its  growth,  but  the 
fruit  which  sustains  life  must  have  its  bud  prepared 
before  the  approach  of  winter,  its  blossom  expanded 
in  the  spring,  and  its  juices  elaborated  by  the  light 
and  heat  of  the  summer  and  the  autumnal  sun. 

In  the  century  which  preceded  the  birth  of  New- 
ton the  science  of  astronomy  advanced  with  the 
most  rapid  steps.  Emerging  from  the  darkness  of 
the  middle  ages,  the  human  mind  seemed  to  rejoice 
in  its  new-born  strength,  and  to  apply  itself  with 
elastic  vigour  to  unfold  the  mechanism  of  the  heavens. 
The  labours  of  Hipparchus  and  Ptolemy  had  indeed 
furnished  many  important  epochs  and  supplied  many 
valuable  data ;  but  the  cumbrous  appendages  of 
cycles  and  epicycles  with  which  they  explained  the 
stations  and  retrogradations  of  the  planets,  and  the 
vulgar  prejudices  which  a  false  interpretation  of 
Scripture  had  excited  against  a  belief  in  the  motion 
of  the  earth,  rendered  it  difficult  even  for  great 
minds  to  escape  from  the  trammels  of  authority, 
and  appeal  to  the  simplicity  of  nature. 

The  sovereign  of  Castile,  the  generous  and  noble- 
minded  Alphonso,  had  long  before  proscribed  the 
rude  expedients  of  his  predecessors ;  and  when  he 
declared  that  if  the  heavens  were  thus  constituted, 
he  could  have  given  the  Deity  good  advice,  he  must 
not  only  have  felt  the  absurdity  of  the  prevailing 
system,  but  must  have  obtained  some  foresight  of  a 
more  simple  arrangement.  But  neither  he  nor  the 
astronomers  whom  he  so  liberally  protected  seem  to 


112  SIR   ISAAC   NEWTON. 

have  established  a  better  system,  and  it  was  left 
to  Copernicus  to  enjoy  the  dignity  of  being  the 
restorer  of  astronomy. 

This  great  man,  a  native  of  Thorn  in  Prussia,  fol- 
lowing his  father's  profession,  began  his  career  as  a 
doctor  of  medicine,  but  an  accidental  attendance  on 
the  mathematical  lectures  of  Brudzevius  excited  a 
love  for  astronomy,  which  became  the  leading  pas- 
sion of  his  life.  Quitting  a  profession  uncongenial 
to  such  pursuits,  he  went  to  Bologna  to  study 
astronomy  under  Dominic  Maria ;  and  after  having 
enjoyed  the  friendship  and  instruction  of  that  able 
philosopher,  he  established  himself  at  Rome  in  the 
humble  situation  of  a  teacher  of  mathematics.  Here 
he  made  numerous  astronomical  observations  which 
served  him  as  the  basis  of  future  researches ;  but 
an  event  soon  occurred  which,  though  it  interrupted 
for  a  while  his  important  studies,  placed  him  in  a 
situation  for  pursuing  them  with  new  zeal.  The 
death  of  one  of  the  canons  enabled  his  uncle,  who 
was  Bishop  of  Ermeland,  to  appoint  him  to  a  can- 
onry  in  the  chapter  of  Frauenburg,  where,  in  a 
house  situated  on  the  brow  of  a  mountain,  he  con- 
tinued, in  peaceful  seclusion,  to  carry  on  his  astro- 
nomical observations.  During  his  residence  at  Rome 
his  talents  had  been  so  well  appreciated,  that  the 
Bishop  of  Fossombrona,  who  presided  over  the 
council  for  reforming  the  calendar,  solicited  the  aid 
of  Copernicus  in  this  desirable  undertaking.  At  first 
he  entered  warmly  into  the  views  of  the  council, 
and  charged  himself  with  the  determination  of  the 
length  of  the  year  and  of  the  month,  and  of  the 
other  motions  of  the  sun  and  moon  that  seemed  to 
be  required ;  but  he  found  the  task  too  irksome,  and 
probably  felt  that  it  would  interfere  with  those 
interesting  discoveries  which  had  already  begun  to 
dawn  upon  his  mind. 

Copernicus  is  said  to  have  commenced  his  inqui- 
ries by  an  historical  examination  of  the  opinions  of 


COPERNICUS.  13 

ancient  authors  on  the  system  of  the  universe  ;  buf 
it  is  more  likely  that  he  sought  for  the  authority  of 
I  their  great  names  to  countenance  liis  peculiar  views, 
and  that  he  was  more  desirous  to  present  his  own 
theory  as  one  that  he  had  received,  rather  than  as 
one  which  he  had  invented.  His  mind  had  been 
long  imbued  with  the  idea  that  simplicity  and  har- 
mony should  characterize  the  arrangements  of  the 
planetary  system,  and,  in  the  complication  and  dis- 
order which  reigned  in  the  hypothesis  of  Ptolemy, 
he  saw  insuperable  objections  to  its  being  regarded 
as  a  representation  of  nature.  In  the  opinions  of 
the  Egyptian  sages,  in  those  of  Pythagoras,  Philo- 
laus,  Aristarchus,  and  Nicetas,  he  recognised  his 
own  earliest  conviction  that  the  earth  was  not  the 
centre  of  the  universe  ;  but  he  appears  to  have  con- 
sidered it  as  still  possible  that  our  globe  might  per- 
form some  function  in  the  system  more  important 
than  that  of  the  other  planets;  and  his  attention 
was  much  occupied  with  the  speculation  of  Martia- 
nus  Capella,  who  placed  the  sun  between  Mars  and 
the  moon,  and  made  Mercury  and  Venus  revolve 
round  him  as  a  centre;  and  with  the  system  of 
Apollonius  Pergaeus,  who  made  all  the  planets  re- 
volve round  the  sun,  while  the  sun  and  moon  were 
carried  round  the  earth  in  the  centre  of  the  universe. 
The  examination,  however,  of  these  hypotheses 
gradually  dispelled  the  difficulties  with  which  the 
subject  was  beset ;  and  after  the  labours  of  more 
than  thirty  years,  he  was  permitted  to  see  the  true 
system  of  the  heavens.  The  sun  he  considered  as 
immoveable  in  the  centre  of  the  system,  while  the 
earth  revolved  between  the  orbits  of  Venus  and 
Mars,  and  produced  by  its  rotation  about  its  axis  all 
the  diurnal  phenomena  of  the  celestial  sphere.  The 
precession  of  the  equinoxes  was  thus  referred  to  a 
slight  motion  of  the  earth's  axis,  and  the  stations 
and  retrogradations  of  the  planets  were  the  neces- 
sary consequence  of  their  own  motions  combined 
K2 


114  SIR   ISAAC   NEWTON. 

with  that  of  the  earth  about  the  sun.  These  re- 
markable views  were  supported  by  numerous  as- 
tronomical observations;  and  in  1530  Copernicus 
brought  to  a  close  his  immortal  work  on  the  Revolu- 
tions of  the  Heavenly  Bodies. 

But  while  we  admire  the  genius  which  triumphed 
over  so  many  difficulties,  we  cannot  fail  to  commend 
the  extraordinary  prudence  with  which  he  ushered 
his  new  system  into  the  world.  Aware  of  the  preju- 
dices, and'  even  of  the  hostility  with  which  such  a 
system  would  be  received,  he  resolved  neither  to 
startle  the  one  nor  provoke  the  other.  He  allowed 
his  opinions  to  circulate  in  the  slow  current  of  per- 
sonal communication.  The  points  of  opposition 
which  they  presented  to  established  doctrines  were 
gradually  worn  down,  and  they  insinuated  them- 
selves into  reception  among  the  ecclesiastical  circles 
by  the  very  reluctance  of  their  author  to  bring  them 
into  notice.  In  the  year  1534,  Cardinal  Schonberg, 
Bishop  of  Capua,  and  Gyse,  Bishop  of  Culm,  exerted 
all  their  influence  to  induce  Copernicus  to  lay  his 
system  before  the  world ;  but  he  resisted  their  so- 
licitations ;  and  it  was  not  till  1539  that  an  accidental 
circumstance  contributed  to  alter  his  resolution. 
George  Rheticus,  professor  of  mathematics  at  Wir- 
temberg,  having  heard  of  the  labours  of  Copernicus, 
resigned  his  chair,  and  repaired  to  Frauenberg  to 
make  himself  master  of  his  discoveries.  This  zeal- 
ous disciple  prevailed  upon  his  master  to  permit  the 
publication  of  his  system ;  and  they  seem  to  have 
arranged  a  plan  for  giving  it  to  the  world  without 
alarming  the  vigilance  of  the  church,  or  startling 
the  prejudices  of  individuals.  Under  the  disguise 
of  a  student  of  mathematics,  Rheticus  published  in 
1540  an  account  of  the  manuscript  volume  of  Coper- 
nicus. This  pamphlet  was  received  without  any 
disapprobation,  and  its  author  was  encouraged  to 
reprint  it  at  Basle,  in  1541,  with  his  own  name. 
The  success  of  these  publications,  and  the  flattering 


TYCHO    BRAKE.  115 

manner  in  which  the  new  astronomy  was  received 
by  several  able  writers,  induced  Copernicus  to  place 
his  MSSj  in  the  hands  of  Rheticus.  It  was  accord- 
ingly printed  at  the  expense  of  Cardinal  Schon- 
berg,  and  appeared  at  Nuremberg  in  1543.  Its  illus- 
trious author,  however,  did  not  live  to  peruse  it. 
A  complete  copy  was  handed  to  him  in  his  last 
moments,  and  he  saw  and  touched  it  a  few  hours 
before  his  death.  This  great  work  was  dedicated 
to  the  Holy  Pontiff,  in  order,  as  Copernicus  himself 
says,  that  the  authority  of  the  head  of  the  church 
might  silence  the  calumnies  of  individuals  who  had 
attacked  his  views  by  arguments  drawn  from  reli- 
gion. Thus  introduced,  the  Copernican  system  met 
with  no  ecclesiastical  opposition,  and  gradually  made 
its  way  in  spite  of  the  ignorance  and  prejudices 
of  the  age. 

Among  the  astronomers  who  provided  the  mate- 
rials of  the  Newtonian  philosophy  the  name  of 
Tycho  Brahe  merits  a  conspicuous  place.  De- 
scended from  an  ancient  Swedish  family,  he  was 
born  at  Knudstorp,  in  Norway,  in  1546,  three  years 
after  the  death  of  Copernicus.  The  great  eclipse 
of  the  sun  which  happened  on  the  26th  August, 
1560,  while  he  was  at  the  University  of  Copenhagen, 
attracted  his  notice :  and  when  he  found  that  all 
its  phenomena  had  been  accurately  predicted,  he 
was  seized  with  the  most  irresistible  passion  to  ac- 
quire the  knowledge  of  a  science  so  infallible  in  its 
results.  Destined  for  the  profession  of  the  law,  his 
friends  discouraged  the  pursuit  which  now  engrossed 
his  thoughts;  and  such  were  the  reproaches  and 
even  persecutions  to  which  he  was  exposed,  that  he 
quitted  his  country  with  the  design  of  travelling 
through  Germany.  At  the  very  commencement  of 
his  journey,  however,  an  event  occurred  in  which 
the  impetuosity  of  his  temper  had  nearly  cost  him 
his  life.  At  a  wedding-feast  in  Rostock,  a  question- 
able point  in  geometry  involved  him  in  a  dispute 


116  SIR   ISAAC  NEWTON. 

with  a  Banish  nobleman  of  the  same  temperament 
with  himself ;  and  the  two  mathematicians  B^solved 
to  settle  the  difference  by  the  sword.  /Tycjio, 
however,  seems  to  have  been  second  in  the  conflict, 
for  he  lost  the  greater  part  of  his  nose,  and  was 
obliged  to  supply  its  place  by  a  substitute  of  gold 
and  silver,  which  a  cement  of  glue  attached  to  his 
face.  ^During  his  stay  at  Augsburg  lie  inspired  the 
burgomaster  of  the  city,  Peter  Hainzell,  with  a  love 
of  astronomy.  This  public-spirited  citizen  erected 
an  excellent  observatory  at  his  own  expense,  and 
here  Tycho  began  that  distinguished  career  which 
has  placed  him  in  the  first  rank  of  practical  as- 
tronomers. 

Upon  his  return  to  Copenhagen  in  1570,  he  was 
received  with  every  mark  of  respect.  The  king  in- 
vited him  to  court,  and  persons  of  all  ranks  harassed 
him  with  their  attentions.  At  Herritzvold,  near  his 
native  place,  the  house  of  his  maternal  uncle  afforded 
him  a  retreat  from  the  gayeties  of  the  capital,  and 
he  was  there  offered  every  accommodation  for  the 
prosecution  of  his  astronomical  studies.  Here, 
however,  the  passion  of  love  and  the  pursuits  of 
alchymy  distracted  his  thoughts ;  but  though  the 
peasant  girl  of  whom  he  was  enamoured  was  of 
easier  attainment  than  the  philosopher's  stone,  the 
marriage  produced  an  open  quarrel  with  his  relations, 
which  it  required  the  interference  of  the  king  to  allay. 
In  the  tranquillity  of  domestic  happiness,  Tycho  re- 
sumed his  study  of  the  heavens,  and  in  1572  he 
enjoyed  the  singular  good  fortune  of  observing, 
through  all  its  variations,  the  new  star  in  Cassiopeia, 
which  appeared  with  such  extraordinary  splendour 
as  to  be  visible  in  the  daytime,  and  which  gradually 
disappeared  in  the  following  year. 

Dissatisfied  with  his  residence  in  Denmark,  Tycho 
resolved  to  settle  in  some  distant  country ;  and  hav- 
ing gone  as  far  as  Venice  in  search  of  a  suitable 
residence,  he  at  last  fixed  upon  Basle,  in  Switzer* 


TYCHO   BRAKE.  117 

land.  The  King  of  Denmark,  however,  had  learned 
his  intention  from  the  Prince  of  Hesse ;  and  when 
Tycho  returned  to  Copenhagen  to  remove  his  family 
and  his  instruments,  his  sovereign  announced  to  him 
his  resolution  to  detain  him  in  his  kingdom.  He 
presented  him  with  j  the  canonry  of  Roschild,  with 
an  income  of  2000  crowns  per  annum.  To  this  he 
added  a  pension  of  1000  crowns ;  and  he  promised 
to  give  him  the  island  of  Huen,  with  a  complete 
observatory  erected  under  his  own  eye.  This  gene- 
rous offer  was  instantly  accepted.  The  celebrated 
observatory  of  Uraniburg  was  established  at  the 
expense  of  about  20,000/. ;  and  in  this  magnificent 
retreat  Tycho  continued  for  twenty-one  years  to  en- 
rich astronomy  with  the  most  valuable  observations. 
Admiring  disciples  crowded  to  this  sanctuary  of  the 
sciences  to  acquire  the  knowledge  of  the  heavens ; 
and  kings*  and  princes  felt  themselves  honoured 
by  becoming  the  guests  of  the  great  astronomer  of 
the  age. 

One  of  the  principal  discoveries  of  Tycho  was 
that  of  the  inequality  of  the  moon's  motion,  called 
the  variation.  He  detected,  also,  the  annual  equa- 
tion which  affects  the  place  of  her  apogee  and  nodes, 
and  he  determined  the  greatest  and  the  least  inclina- 
tion of  the  lunar  orbit.  His  observations  on  the 
planets  were  numerous  and  precise,  and  have  formed 
the  data  of  the  present  generalizations  in  astronomy. 

*  When  James  I.  went  to  Copenhagen  in  1590,  to'conclude  his  mar- 
riage with  the  Princess  Anne  of  Denmark,  he  spent  eight  days  under 
the  roof  of  Tycho  at  Uranihurg.  As  a  token  of  his  gratitude,  he  com- 
posed a  set  of  Latin  verses  in  honour  of  the  astronomer,  and  left  him  a 
magnificent  present  at  his  departure.  He  gave  him  also  his  royal  license 
for  the  publication  of  his  works  in  England,  and  accompanied  it  with 
the  following  complimentary  letter : — 

"  Nor  am  I  acquainted  with  these  things  on  the  relation  of  others,  or 
from  a  mere  perusal  of  your  works,  but  I  have  seen  them  with  my  own 
eyes,  and  heard  them  with  my  own  ears,  in  your  residence  at  Urani 
burg,  during  the  various  learned  and  agreeable  conversations  which  I 
there  held  with  you,  which  even  now  affect  my  mind  to  such  a  degree, 
that  it  is  difficult  to  decide  whether  I  recollect  them  with  greater  pleasure 
or  admiration." 


118  SIR   ISAAC   NEWTON. 

Though  thus  skilful  in  the  observation  of  phenomena, 
his  mind  was  but  little  suited  to  investigate  their 
cause,  and  it  was  probably  owing  to  this  defect  that 
he  rejected  the  system  of  Copernicus.  The  vanity 
of  giving  his  own  name  to  another  system  was  not 
likely  to  actuate  a  mind  such  as  his,  and  it  was  more 
probable  that  he  was  led  to  adopt  the  immobility  of 
the  earth,  and  to  make  the  sun,  with  all  his  attendant 
planets,  circulate  round  it,  from  the  great  difficulty 
which  still  presented  itself  by  comparing  the  apparent 
diameter  of  the  stars  with  the  annual  parallax  of  the 
earth's  orbit. 

The  death  of  Frederick  in  1588  proved  a  severe 
calamity  to  Tycho,  and  to  the  science  which  he  cul- 
tivated. During  the  first  years  of  the  minority  of 
Christian  IV.  the  regency  continued  the  royal  patron- 
age to  the  observatory  of  Uraniburg;  and  in  1592 
the  young  king  paid  a  visit  of  some  days  to  Tycho, 
and  left  him  a  gold  chain  in  token  of  his  favour. 
The  astronomer,  however,  had  made  himself  enemies 
at  court,  and  the  envy  of  his  high  reputation  had 
probably  added  fresh  malignity  to  the  irritation  of 
personal  feelings.  Under  the  ministry  of  Wolchen- 
dorf,  a  name  for  ever  odious  to  science,  Tycho's 
pension  was  stopped ; — he  was  in  1597  deprived  of 
the  canonry  of  Roschild,  and  was  thus  forced,  with 
his  wife  and  children,  to  seek  an  asylum  in  a  foreign 
land.  His  friend,  Henry  Rantzau,  of  Wansbeck, 
under  whose  roof  he  found  a  hospitable  shelter,  was 
fortunately  acquainted  with  the  emperor  Rodolph  II., 
who,  to  his  love  of  science,  added  a  passion  for 
alchymy  and  astrology.  The  reputation  of  Tycho 
having  already  reached  the  imperial  ear,  the  recom- 
mendation of  Rantzau  was  scarcely  necessaiy  to  en- 
sure him  his  warmest  friendship.  Invited  by  the  em- 
peror, he  repaired  in  1599  to  Prague,  where  he  met 
with  the  kindest  reception.  A  pension  of  three 
thousand  crowns  was  immediately  settled  upon  him, 
and  a  commodious  observatory  erected  for  his  use 


TYCHO  BRAKE.  119 

In  the  vicinity  of  that  city.  Here  the  exiled  astrono- 
mer renewed  with  delight  his  interrupted  labours, 
and  the  gratitude  which  he  cherished  for  the  royal 
favour  increased  the  satisfaction  which  he  felt  in 
having  so  unexpectedly  found  3.  resting-place  for 
approaching  age.  These  prospects  of  better  days 
were  enhanced  by  the  good  fortune  of  receiving  two 
such  men  as  Kepler  and  Longomontanus  for  his 
pupils ;  but  the  fallacy  of  human  anticipation  was 
here,  as  in  so  many  other  cases,  strikingly  displayed. 
Tycho  was  not  aware  of  the  inroads  which  both  his 
labours  and  his  disappointments  had  made  upon  his 
constitution.  Though  surrounded  with  affectionate 
friends  and  admiring  disciples,  he  was  still  an  exile 
in  a  foreign  land.  Though  his  country  had  been 
base  in  its  ingratitude,  it  was  yet  the  land  which  he 
loved, — the  scene  of  his  earliest  affection, — the 
theatre  of  his  scientific  glory.  These  feelings  con- 
tinually preyed  upon  his  mind,  and  his  unsettled 
spirit  was  ever  hovering  among  his  native  mountains. 
In  this  condition  he  was  attacked  with  a  disease  of 
the  most  painful  kind,  and  though  the  paroxysms  of 
its  agonies  had  lengthened  intermissions,  yet  he  saw 
that  death  was  approaching.  He  implored  his  pupils 
to  persevere  in  their  scientific  labours.  He  conversed 
with  Kepler  on  some  of  the  profoundest  points  of 
astronomy,  and  with  these  secular  occupations  he 
mingled  frequent  acts  of  piety  and  devotion.  In 
this  happy  condition  he  expired  without  pain  at  the 
age  of  fifty-five,  the  unquestionable  victim  of  the 
councils  of  Christian  IV. 

Notwithstanding  the  accessions  which  astronomy 
had  received  from  the  labours  of  Copernicus  and 
Tycho,  no  progress  was  'yet  made  in  developing 
the  general  laws  of  the  system,  and  scarcely  an  idea 
had  been  formed  of  the  power  by  which  the  planets 
were  retained  in  their  orbits.  The  labours  of  as- 
siduous observers  had  supplied  the  materials  for  this 


120  SIR   ISAAC   NEWTON. 

purpose,  and  Kepler  arose  to  lay  the  foundations  of 
physical  astronomy. 

John  Kepler  was  born  at  Wiel,  in  Wirtemberg,  in 
1571.  He  was  educated  for  the  church,  and  dis- 
charged even  some  of  the  clerical  functions;  but  his 
devotion  to  science  withdrew  him  from  the  study  of 
theology.  Having  received  mathematical  instruc- 
tion from  the  celebrated  Maestlinus,  he  had  made 
such  progress  in  the  science,  that  he  was  invited  in 
1594  to  fill  the  mathematical  chair  of  Gratz  in  Sty- 
ria.  Endowed  with  a  fertile  imagination,  his  mind 
was  ever  intent  upon  subtle  and  ingenious  specula- 
tions. In  the  year  1596  he  published  his  peculiar 
views  in  a  work  on  the  Harmonies  and  Analogies  of 
Nature.  In  this  singular  production,  he  attempts  to 
solve  what  he  calls  the  great  cosmographical  mys- 
tery of  the  admirable  proportion  of  the  planetary 
orbits ;  and  by  means  of  the  six  regular  geometrical 
solids,*  he  endeavours  to  assign  a  reason  why  there 
are  six  planets,  and  why  the  dimensions  of  their 
orbits  and  the  time  of  their  periodical  revolutions 
were  such  as  Copernicus  had  found  them..  If  a 
cube,  for  example,  were  inserted  in  a  sphere,  of  which 
Saturn's  orbit  was  one  of  the  great  circles,  it  would, 
he  supposed,  touch  by  its  six  planes  the  lesser 
sphere  of  Jupiter ;  and,  in  like  manner,  he  proposes 
to  determine,  by  the  aid  of  the  other  geometrical 
solids,  the  magnitude  of  the  spheres  of  the  other 
planets.  A  copy  of  this  work  was  presented  by  its 
author  to  Tycho  Brahe,  who  had  been  too  long 
versed  in  the  severe  realities  of  observation  to  at- 
tach any  value  to  such  wild  theories.  He  advised 
his  young  friend  "  first  to  lay  a  solid  foundation  for 
his  views  by  actual  observation,  and  then,  by  ascend- 
ing from  these,  to  strive  to  reach  the  causes  of 
things ;"  and  there  is  reason  to  think  that,  by  the  aid 
of  the  whole  Baconian  philosophy,  thus  compressed 

*  The  cube,  the  sphere,  the  tetrahedron,  the  octahedron,  the  dodeca- 
hedron, and  the  icosahedron. 


KEPLER.  121 

by  anticipation  into  a  single  sentence,  he  abandoned 
for  a  while  his  visionary  inquiries. 

In  the  year  1598  Kepler  suffered  persecution  for 
his  religious  principles,  and  was  compelled  to  quit 
Gratz ;  but  though  he  was  recalled  by  the  States  of 
Styria,  he  felt  his  situation  insecure,  and  accepted  of 
a  pressing  invitation  from  Tycho  to  settle  at  Prague, 
and  assist  him  in  his  calculations.  Having  arrived 
in  Bohemia  in  1600,  he  was  introduced  by  his  friends 
to  the  Emperor  Rodplph,  from  whom  he  ever  after- 
ward received  the  kindest  attention.  On  the  death 
of  Tycho  in  1601,  he  was  appointed  mathematician 
to  the  emperor, — a  situation  in  which  he  was  con- 
tinued during  the  successive  reigns  of  Matthias  and 
Ferdinand;  but  what  was  of  more  importance  to 
science,  he  was  put  in  possession  of  the  valuable 
collection  of  Tycho's  observations.  These  obser- 
vations were  remarkably  numerous ;  and  as  the  orbit 
of  Mars  was  more  oval  than  that  of  any  of  the  other 
planets,  they  were  peculiarly  suitable  for  determin- 
ing its  real  form.  The  notions  of  harmony  and 
symmetry  in  the  construction  of  the  solar  system, 
which  had  filled  the  mind  of  Kepler,  necessarily  led 
him  to  believe  that  the  planets  revolved  with  a  uni- 
form motion  in  circular  orbits.  So  firm,  indeed,  was 
this  conviction,  that  he  made  numerous  attempts  to 
represent  the  observations  of  Tycho  by  this  hy- 
pothesis. The  deviations  were  too  great  to  be  as- 
cribed to  errors  of  observation ;  and  in  trying  various 
other  curves,  he  was  led  to  the  discovery  that  Mars 
revolved  round  the  sun  in  an  elliptical  orbit,  in  one 
of  the  foci  of  which  the  sun  itself  was  placed.  The 
same  observations  enabled  him  to  determine  the 
dimensions  of  the  planet's  orbit,  and  by  comparing 
together  the  times  in  which  Mars  passed  over 
different  portions  of  its  orbit,  he  found  that  they 
were  to  one  another  as  the  areas  described  by  the 
lines  drawn  from  the  centre  of  the  planet  to  the 
centre  of  the  sun,  or,  in  more  technical  terms,  that 
L 


122  SIR   ISAAC   NEWTON. 

the  radius  vector  describes  equal  areas  in  equal 
times.  These  two  remarkable  discoveries,  the  nrst 
that  were  ever  made  in  physical  astronomy,  were 
extended  to  all  the  other  planets  of  the  system,  and 
were  communicated  to  the  world  in  1609,  in  his 
"  Commentaries  on  the  Motions  of  the  Planet  Mars, 
as  deduced  from  the  observations  of  Tycho  Brahe." 
Although  our  author  was  conducted  to  these  great 
laws  by  the  parent  examination  of  well-established 
facts,  his  imagination  was  ever  hurrying  him  among 
the  wilds  of  conjecture.  Convinced  that  the  mean 
distances  of  the  planets  from  the  sun  bore  to  one 
another  some  mysterious  relation,  he  not  only  com- 
pared them  with  the  regular  geometrical  solids,  but 
also  with  the  intervals  of  musical  tones ;  an  idea 
which  the  ancient  Pythagoreans  had  suggested,  and 
which  had  been  adopted  by  Archimedes  himself. 
All  these  comparisons  were  fruitless ;  and  Kepler 
was  about  to  abandon  an  inquiry  of  about  seventeen 
years'  duration,  when,  on  the  8th  March,  1618,  he 
conceived  the  idea  of  comparing  the  powers  of  the 
different  members  which  express  the  planetary  dis- 
tances, in  place  of  the  numbers  themselves.  He 
compared  the  squares  and  the  cubes  of  the  distances 
with  the  same  powers  of  the  periodic  times  ;  nay,  he 
tried  even  the  squares  of  the  times  with  the  cubes 
of  the  distances ;  but  his  hurry  and  impatience  led 
him  into  an  error  of  calculation,  and  he  rejected  this 
law  as  having  no  existence  in  nature  !  On  the  15th 
May,  his  mind  again  reverted  to  the  same  notion, 
and  upon  making  the  calculations  anew,  and  free  from 
error,  he  discovered  the  great  law,  that  the  squares 
of  the  periodic  times  of  any  two  planets  are  to  one 
another  as  the  cubes  of  their  distances  from  the  sun. 
Enchanted  with  this  unexpected  result,  he  could 
scarcely  trust  his  calculations ;  and,  to  use  his  own 
language,  he  at  first  believed  that  he  was  dreaming, 
and  had  taken  for  granted  the  very  truth  of  which 
he  was  in  search.  This  brilliant  discovery  was  pub- 


KEPLER.  123 

lished  in  1619,  in  his  "Harmony  of  the  World';"  a 
I  work  dedicated  to  James  VI.  of  Scotland.  Thus 
!  were  established  what  have  been  called  the  three 
i  laws  of  Kepler, — the  motion  of  the  planets  in  ellip- 
<  tical  orbits, — the  proportionality  between  the  areas 
•  described  and  their  times  of  description, — and  the 
•relations  between  the  squares  of  the  periodic  times 
!'  and  the  cubes  of  the  distances. 

The  relation  of  the  movements  of  the  planets  to 
the  sun,  as  the  general  centre  of  all  their  orbits, 
could  not  fail  to  suggest  to  Kepler  that  some  power 
resided  in  that  luminary  by  which  these  various  mo- 
tions were  produced ;  and  he  went  so  far  as  to  con- 
jecture that  this  power  diminishes  as  the  square  of 
jj  the  distance  of  the  body  on  which  it  was  exerted ; 
i  but  he  immediately  rejects  this  law,  and  prefers  that 
of  the  simple  distances.     In  his  work  on  Mars,  he 
?  speaks  of  gravity  as  a  mutual  and  corporeal  affec- 
tion between  similar  bodies.     He  maintained  that 
the  tides  were  occasioned  by  the  moon's  attraction, 
and  that  the  irregularities  of  the  lunar  motions,  as 
detected  by  Tycho,  were  owing  to  the  joint  actions 
of  the  sun  and  the  earth ;  but  the  relation  between 
gravity,  as  exhibited  on  the  earth's  surface,  and  as 
1  conducting  the   planets   in   their   orbits,  required 
more  patience  of  thought  than  he  could  command, 
and  was  accordingly  left  for  the  exercise  of  higher 
powers. 

The  misery  in  which  Kepler  lived  forms  a  painful 
I  contrast  with  the  services  which  he  performed  to 
science.  The  pension  on  which  he  subsisted  was 
always  in  arrears,  and  though  the  three  emperors 
whose  reigns  he  adorned  directed  their  ministers 
to  be  more  punctual  in  its  payment,  the  disobe- 
dience of  their  commands  was  a  source  of  continued 
vexation  to  Kepler.  When  he  retired  to  Sagan,  in 
Silesia,  to  spend  in  retirement  the  remainder  of  his 
days,  his  pecuniary  difficulties  became  still  more 
harassing.  Necessity  at  last  compelled  him  to  apply 


124  SIR  ISAAC   NEWTON. 

personally  for  the  arrears  which  were  due ;  and  he 
accordingly  set  out  in  1630  for  Ratisbon;  but  in 
consequence  of  the  great  fatigue  which  so  long  a 
journey  on  horseback  produced,  he  was  seized  with 
a  fever,  which  carried  him  off  on  the  30th  Novem- 
ber, 1630,  in  the  59th  year  of  his  age. 

While  Kepler  was  thus  laying  the  foundation  of 
physical  astronomy,  Galileo  was  busily  employed  in 
extending  the  boundaries  of  the  solar  system.  This 
distinguished  philosopher  was  born  at  Pisa  in  1564. 
He  was  the  son  of  a  Florentine  nobleman,  and  was 
educated  for  the  medical  profession ;  but  a  passion 
for  geometry  took  possession  of  his  mind,  and  called 
forth  all  his  powers.  Without  the  aid  of  a  master, 
he  studied  the  writings  of  Euclid  and  of  Archimedes;; 
and  such  were  his  acquirements,  that  he  was  ap- 
pointed by  the  Grand-duke  of  Tuscany  to  the  mathe- 
matical chair  of  Pisa  in  the  twenty-fifth  year  of  his 
age.  His  opposition  to  the  Aristotelian  philosophy 
gained  him  many  enemies,  and  at  the  end  of  three 
years  he  quitted  Pisa,  and  accepted  of  an  invitation 
to  the  professorship  of  mathematics  at  Padua.  Here 
he  continued  for  eighteen  years  adorning  the  uni- 
versity by  his  name,  and  diffusing  around  him  a 
taste  for  the  physical  sciences.  With  the  excep- 
tion of  some  contrivances  of  inferior  importance, 
Galileo  had  distinguished  himself  by  no  discovery 
till  he  had  reached  the  forty-fifth  year  of  his  age. 
In  the  year  1609,  the  same  year  in  which  Kepler 
published  his  celebrated  commentary  on  Mars,  Gali- 
leo paid  a  visit  to  Venice,  where  he  heard,  in  the 
course  of  conversation,  that  a  Dutchman  of  the 
name  of  Jansens  had  constructed  and  presented  to 
Prince  Maurice  an  instrument  through  which  he  saw 
distant  objects  magnified  and  rendered  more  distinct, 
as  if  they  had  been  brought  nearer  to  the  observer. 
This  report  was  credited  by  some  and  disbelieved 
by  others ;  but,  in  the  course  of  a  few  days,  Galileo 
received  a  letter  from  James  Badovere  at  Paris, 


GALILEO.  120 

which  placed  beyond  a  doubt  the  existence  of  such 
an  instrument.  The  idea  instantly  filled  his  mind 
as  one  of  the  utmost  importance  to  science ;  and  so 
thoroughly  was  he  acquainted  with  the  properties 
of  lenses,  that  he  not  only  discovered  the  principle 
of  its  construction,  but  was  able  to  complete  a  tele- 
scope for  his  own  use.  Into  one  end  of  a  leaden 
tube  he  fitted  a  spectacle-glass  plane  on  one  side 
and  convex  on  the  other,  and  in  the  other  end  he 
placed  another  spectacle-glass  concave  on  one  side 
and  plane  on  the  other.  He  then  applied  his  eye 
to  the  concave  glass,  and  saw  objects  "pretty  large 
and  pretty  near  him."  They  appeared  three  times 
nearer,  and  nine  times  larger  in  surface,  than  to  the 
naked  eye.  He  soon  after  made  another,  which 
represented  objects  above  sixty  times  larger ;  and, 
sparing  neither  labour  nor  expense,  he  finally  con- 
structed an  instrument  so  excellent,  as  "to  show 
things  almost  a  thousand  times  larger,  and  above 
thirty  times  nearer  to  the  naked  eye." 

There  is,  perhaps,  no  invention  that  science  has 
presented  to  man  so  extraordinary  in  its  nature,  and 
|  so  boundless  in  its  influence,  as  that  of  the  tele- 
I  scope.  To  the  uninstructed  mind,  the  power  of 
jj  seeing  an  object  a  thousand  miles  distant,  as  large 
I  and  nearly  as  distinct  as  if  it  were  brought  within 
I  a  mile  of  ,the  observer,  must  seem  almost  miracu- 
t  lous ;  and  to  the  philosopher,  even,  who  thoroughly 
1  comprehends  the  principles  upon  which  it  acts,  it 
I  must  ever  appear  one  of  the  most  elegant  applica* 
|  tions  of  science.  To  have  been  the  first  astronomer 
|i  in  whose  hands  such  a  gift  was  placed  wras  a  prefer- 
i|  ence  to  which  Galileo  owed  much  of  his  future 
reputation. 

No  sooner  had  he  completed  his  telescope  than 
he  applied  it  to  the  heavens,  and  on  the  7th  Janu- 
ary, 1618,  the  first  day  of  its  use,  he  saw  round 
Jupiter  three  bright  little  stars  lying  in  a  line  par- 
allel to  the  ecliptic,  two  to  the  east,  and  one  to  the 
L2 


126  SIR  ISAAC   NEWTON. 

west  of  the  planet.  Regarding  them  as  ordinary 
stars,  he  never  thought  of  estimating  their  distances. 
On  the  following  day,  when  he  accidentally  directed 
his  telescope  to  Jupiter,  he  was  surprised  to  see 
the  three  stars  to  the  west  of  the  planet.  To  pro- 
duce this  effect  it  was  requisite  that  the  motion  of 
Jupiter  should  be  direct,  though,  according  to  calcu- 
lation, it  was  actually  retrograde.  In  this  dilemma 
he  waited  with  impatience  for  the  evening  of  the 
9th,  but  unfortunately  the  sky  was  covered  with 
clouds.  On  the  10th  he  saw  only  two  stars  to  the 
east — a  circumstance  which  he  was  no  longer  able 
to  explain  by  the  motion  of  Jupiter.  He  was  there- 
fore compelled  to  ascribe  the  change  to  the  stars 
themselves ;  and  upon  repeating  his  observations 
on  the  llth,  he  no  longer  doubted  that  he  had  dis- 
covered three  planets  revolving  round  Jupiter.  On 
the  13th  January  he  for  the  first  time  saw  the 
fourth  satellite.* 

This  discovery,  though  of  the  utmost  importance 
in  itself,  derived  an  additional  value  from  the  light 
which  it  threw  on  the  true  system  of  the  universe. 
While  the  earth  was  the  only  planet  enlightened 
by  a  moon,  it  might  naturally  be  supposed  that  it 
alone  was  habitable,  and  was  therefore  entitled  to 
the  pre-eminence  of  occupying  the  centre  of  the 
system ;  but  the  discovery  of  four  moons  round  a 
much  larger  planet  deprived  this  argument  of  its 
force,  and  created  a  new  analogy  between  the  earth 
and  the  other  planets.  When  Kepler  received  the 
"  Sidereal  Messenger,"  the  work  in  which  Galileo 
announced  his  discovery  in  1610,  he  perused  it  with 
the  deepest  interest ;  and  while  it  confirmed  and 
extended  his  substantial  discoveries,  it  dispelled  at; 
the  same  time  some  of  those  harmonic  dreams  which 
still  hovered  among  his  thoughts.  In  the  "Dis- 

*  Simon  Marius,  mathematician  to  the  Marquis  of  Brandenburg, 
assures  us  that  he  discovered  the  satellites  of  Jupiter  in  November 
1609. 


GALILEO.  127 

sertation"  which  he  published  on  the  discovery  of 
Galileo,  he  expresses  his  hope  that  satellites  will 
be  discovered  round  Saturn  and  Mars, — he  conjec- 
tures that  Jupiter  has  a  motion  of  rotation  about 
his  axis,— and  states  his  surprise,  that,  after  what 
had  been  written  on  the  subject  of  telescopes  by 
Baptista  Porta,  they  had  not  been  earlier  introduced 
into  observatories. 

In  continuing  his  observations,  Galileo  applied 
his  telescope  to  Venus,  and  in  1610  he  discovered 
the  phases  of  that  planet,  which  exhibited  to  him 
the  various  forms  of  the  waxing  and  the  waning 
moon.  This  fact  established  beyond  a  doubt  that 
the  planet  revolved  round  the  sun,  and  thus  gave 
an  additional  blow  to  the  Ptolemaic  system.  In  his 
observations  on  the  sun,  Galileo  discovered  his  spots, 
and  deduced  from  them  the  rotation  of  the  central 
luminary.  He  observed  that  the  body  of  Saturn 
had  handles  attached  to  it ;  but  he  was  unable  to 
detect  the  form  of  its  ring,  or  render  visible  its 
minute  satellites.  On  the  surface  of  the  moon  he 
discovered  her  mountains  and  valleys,  and  deter- 
mined the  curious  fact  of  her  libration,  in  virtue  of 
which  parts  of  the  margin  of  her  disk  occasionally 
appear  and  disappear.  In  the  Milky  Way  he  de- 
scried numerous  minute  stars  which  the  unassisted 
eye  was  unable  to  perceive ;  and  as  the  largest  fixed 
stars,  in  place  of  being  magnified  by  the  telescope, 
became  actually  minute  brilliant  points,  he  inferred 
their  immense  distance  as  rendered  necessary  by  the 
Copernican  hypothesis.  All  his  discoveries,  indeed, 
furnished  fresh  arguments  in  favour  of  the  new 
system ;  and  the  order  of  the  planets  and  their  re- 
lation to  a  central  sun  may  now  be  considered  as 
established  by  incontrovertible  evidence. 

While  Galileo  was  occupied  with  these  noble  pur- 
suits at  Pisa,  to  which  he  had  been  recalled  in  1611, 
his  generous  patron,  Cosmo  II.  Grand-duke  of  Tus- 
cany, invited  him  to  Florence,  that  he  might  purmie 


128  SIR    ISAAC   NEWTON. 

with  uninterrupted  leisure  his  astronomical  obser- 
vations, and  carry  on  his  correspondence  with  the 
German  astronomers.  His  fame  had  now  resounded 
through  all  Europe ; — the  strongholds  of  prejudice 
and  ignorance  were  unbarred ;— and  the  most  obsti- 
nate adherents  of  ancient  systems  acknowledged 
the  meridian  power  of  the  day-star  of  science. 
Galileo  was  ambitious  of  propagating  the  great 
truths  which  he  contributed  so  powerfully  to  estab- 
lish. He  never  doubted  that  they  would  be  re- 
ceived with  gratitude  by  all, — by  the  philosopher  as 
the -consummation  of  the  greatest  efforts  of  human 
genius, — and  by  the  Christian  as  the  most  transcend- 
ent displays  of  Almighty  power.  But  he  had  mis- 
taken the  disposition  of  his  species,  and  the  charac- 
ter of  the  age.  That  same  system  of  the  heavens 
which  had  been  discovered  by  the  humble  eccle- 
siastic of  Frauenberg,  which  had  been  patronised  by 
the  kindness  of  a  bishop,  and  .published  at  the  ex- 
pense of  a  cardinal,  and  which  the  pope  himself 
had  sanctioned  by  the  warmest  reception,  was,  after 
the  lapse  of  a  hundred  years,  doomed  to  the  most 
violent  opposition,  as  subversive  of  the  doctrines 
of  the  Christian  faith.  On  no  former  occasion  has 
the  human  mind  exhibited  such  a  fatal  relapse  into 
intolerance.  The  age  itself  had  improved  in  libe- 
rality ; — the  persecuted  doctrines  themselves  had 
become  more  deserving  of  reception ; — the  light  of 
the  Reformed  faith  had  driven  the  Catholics  from 
some  of  their  most  obnoxious  positions ; — and  yet, 
under  all  these  circumstances,  the  church  of  Rome 
unfurled  her  banner  of  persecution  against  the  pride 
of  Italy,  against  the  ornament  of  his  species,  and 
against  truths  immutable  and  eternal. 

In  consequence  of  complaints  laid  before  the  Holy 
Inquisition,  Galileo  was  summoned  to  appear  at 
Rome  in  1615,  to  answer  for  the  heretical  opinions 
which  he  had  promulgated.  He  was  charged  with 
M  maintaining:  as  true  the  false  doctrine  held  by 


GALILEO.  129 

many,  that  the  sun  was  immoveable  in  the  centre 
of  the  world,  and  that  the  earth  revolved  with  a 
diurnal  motion; — with  having  certain  disciples  to 
whom  he  taught  the  same  doctrine ; — with  keeping 
up  a  correspondence  on  the  subject  with  several 
German  mathematicians; — with  having  published 
letters  on  the  solar  spots,  in  which  he  explained  the 
same  doctrine  as  true ; — and  with  having  glossed 
over  with  a  false  interpretation  the  passages  of 
Scripture  which  were  urged  against  it."    The  con- 
sideration of  these  charges  came  before  a  meeting 
of  the  Inquisition,  which  assembled  on  the  25th 
February,  1616 ;  and  the  court,  declaring  their  dis- 
position to  deal   gently  with   the   prisoner,  pro- 
aounced  the  following  decree  :— "  That   Cardinal 
Bellarmine  should  enjoin  Galileo  to  renounce  en- 
;irely  the  above-recited  false  opinions ;  that,  on  his 
'efusal  to  do  so,  he  should  be  commanded  by  the 
commissary  of  the  Inquisition  to  abandon  the  said 
doctrine,  and  to  cease  to  teach  and  defend  it ;  and 
;hat,  if  he  did  not  obey  this  command,  he  should 
>e  thrown  into  prison."    On  the  26th  of  February 
alileo  appeared  before  Cardinal  Bellarmine,  and, 
after  receiving  from  him  a  gentle  admonition,  he 
was  commanded  by  the  commissary,  in  the  presence 
of  a  notary  and  witnesses,  to  desist  altogether  from 
lis  erroneous  opinions ;  and  it  was  declared  to  be 
unlawful  for  him  in  future  to  teach  them  in  any 
way  whatever,  either  orally  or  in  his  writings.    To 
these  commands  Galileo  promised  obedience,  and 
was  dismissed  from  the  Inquisition. 

The  mildness  of  this  sentence  was  no  doubt  partly 
owing  to  the  influence  of  the  Grand-duke  of  Tus- 
cany, and  other  persons  of  rank  and  influence  at  the 
papal  court,  who  took  a  deep  interest  in  the  issue 
of  the  trial.  Dreading,  however,  that  so  slight  a 
punishment  might  not  have  the  eifect  of  putting 
down  the  obnoxious  doctrines,  the  Inquisition  issued 
a  decree  denouncing  the  new  opinions  as  false  and 


130  SIR   ISAAC   NEWTON. 

contrary  to  the  sacred  writings,  and  prohibiting  the 
sale  of  eveiy  book  in  which  they  should  be  main- 
tained. 

Thus  liberated  from  his  persecutors,  Galileo  re- 
turned to  Florence,  where  he  pursued  his  studies 
with  his  wonted  diligence  and  ardour.  The  recanta- 
tion of  his  astronomical  opinions  was  so  formal 
and  unreserved,  that  ordinary  prudence,  if  not  a 
sense  of  personal  honour,  should  have  restrained  him 
from  unnecessarily  bringing  them  before  the  world. 
No  anathema  was  pronounced  against  his  scientific 
discoveries ;  no  interdict  was  laid  upon  the  free 
exercise  of  his  genius.  He  was  prohibited  merely 
from  teaching  a  doctrine  which  the  church  of  Rome 
considered  to  be  injurious  to  its  faith.  We  might 
have  expected,  therefore,  that  a  philosopher  so  con- 
spicuous in  the  eyes  of  the  world  would  have  re- 
spected the  prejudices,  however  base,  of  an  institu- 
tion whose  decrees  formed  part  of  the  law  of  the 
land,  and  which  possessed  the  power  of  life  and 
death  within  the  limits  of  its  jurisdiction.  Galileo, 
however,  thought  otherwise.  A  sense  of  degrada- 
tion* seems  to  have  urged  him  to  retaliate,  and  before 
six  years  had  elapsed,  he  began  to  compose  his 
"  Cosmical  System,  or  Dialogues  on  the  two  greatest 
Systems  of  the  World,  the  Ptolemean  and  the  Co- 
pernican,"  the  concealed  object  of  which  is  to 
establish  the  opinions  which  he  had  promised  to 
abandon.  In  this  work  the  subject  is  discussed  by 
three  speakers,  Sagredo,  Salviatus,  and  Simplicius, 
a  peripatetic  philosopher,  who  defends  the  system  of 

*  It  is  distinctly  stated  in  the  sentence  of  the  Inquisition,  that  Galileo's 
enemies  had  charged  him  with  having  abjured  his  opinions  in  1616,  and 
affirmed  that  he  had  been  punished  by  the  Inquisition.  In  order  to  re- 
fute these  calumnies,  Galileo  applied  to  Cardinal  Bellarmine  for  a  certifi- 
cate to  prove  that  he  neither  abjured  his  opinions  nor  suffered  any  pun- 
ishment for  them ;  but  that  the  doctrine  of  the  motion  of  the  earth  .and 
the  stability  of  the  sun  was  only  denounced  to  him  as  contrary  to  Scrip- 
ture, and  as  one  which  could  not  be  defended  or  maintained.  Cardinal 
Bellarmine  drew  up  such  a  certificate  in  his  own  handwriting. 


GALILEO.  131 

Ptolemy  with  much  skill  against  the  overwhelming 
arguments  of  the  rival  disputants.  Galileo  hoped  to 
escape  notice  by  this  indirect  mode  of  propagating 
the  new  system,  and  he  obtained  permission  to  pub- 
lish his  work,  which  appeared  at  Florence  in  1632. 

The  Inquisition  did  not,  as  might  have  been  ex- 
pected, immediately  summon  Galileo  to  their  pres- 
3nce.  Nearly  a  year  elapsed  before  they  gave  any 
ndication  of  their  design;  and,  according  to  their 
own  statement,  they  did  not  even  take  the  subject 
under  consideration  till  they  saw  that  the  obnoxious 
tenets  were  every  day  gaining  ground,  in  conse- 
quence of  the  publication  of  the  Dialogues.  They 
then  submitted  the  work  to  a  careful  examination, 
and  having  found  it  to  be  a  direct  violation  of  the 
njunction  which  had  been  formerly  intimated  to  its 
author,  they  again  cited  him  before  their  tribunal  in 
1633.  The  venerable  sage,  now  in  his  seventieth 
year,  was  thus  compelled  to  repair  to  Rome,  and 
when  he  arrived  he  was  committed  to  the  apart- 
ments of  the  Fiscal  of  the  Inquisition.  The  un- 
changeable friendship,  however,  of  the  Grand-duke 
of  Tuscany  obtained  a  remission  of  this  severity, 
and  Galileo  was  allowed  to  reside  at  the  house  of 
:he  Tuscan  ambassador  during  the  two  months 
which  the  trial  occupied.  When  brought  before 
ihe  Inquisition,  and  examined  upon  oath,  he  ac- 
knowledged that  the  Dialogues  were  written  by  him- 
self, and  that  he  obtained  permission  to  publish  them 
without  notifying  to  the  person  who  gave  it  that  he 
lad  been  prohibited  from  holding,  defending,  or 
teaching  the  heretical  opinions.  He  confessed  also 
ihat  the  Dialogues  were  composed  in  such  a  manner, 
ihat  the  arguments  in  favour  of  the  Copernican  sys- 
tem, though  given  as  partly  false,  were  yet  managed 
in  such  a  manner  that  they  were  more  likely  to  con- 
firm than  overturn  its  doctrines ;  but  that  this  error, 
which  was  not  intentional,  arose  from  the  natural 
desire  of  making  an  ingenious  defence  of  false  propo- 


132  SIR   ISAAC   NEWTON. 

sitions,  and  of  opinions  that  had  the  semblance  of 
probability. 

After  receiving  these  confessions  and  excuses,  the 
Inquisition  allowed  Galileo  a  proper  time  for  giving1 
in  his  defence ;  but  this  seems  to  have  consisted 
solely  in  bringing  forward  the  certificate  of  Cardinal 
Bellarmine  already  mentioned,  which  made  no  allu- 
sion to  the  promise  under  which  Galileo  had  come 
never  to  defend,  nor  teach  in  any  way  whatever,  the 
Copernican  doctrines.  The  court  held  this  defence 
to  be  an  aggravation  of  the  crime  rather  than  an 
excuse  for  it,  and  proceeded  to  pronounce  a  sentence 
which  will  be  ever  memorable  in  the  history  of  the 
human  mind. 

Invoking  the  name  of  our  Saviour,  they  declare, 
that  Galileo  had  made  himself  liable  to  the  suspicion 
of  heresy,  by  believing  the  doctrine,  contrary  to 
Scripture,  that  the  sun  was  the  centre  of  the  earth's 
orbit,  and  did  not  move  from  east  to  west ;  and  by 
defending  as  probable  the  opinion  that  the  earth 
moved,  and  was  not  the  centre  of  the  world ;  and 
that  he  had  thus  incurred  all  the  censures  and  penal- 
ties which  were  enacted  by  the  church  against  such 
offences  ; — but  that  he  should  be  absolved  from  these 
penalties,  provided  he  sincerely  abjured  and  cursed 
all  the  errors  and  heresies  contained  in  the  formula 
of  the  church,  which  should  be  submitted  to  him. 
That  so  grave  and  pernicious  a  crime  should  not 
pass  altogether  unpunished,  that  he  might  become 
more  cautious  in  future,  and  might  be  an  example 
to  others  to  abstain  from  such  offences,  they  decreed 
that  his  Dialogues  should  be  prohibited  by  a  formal 
edict, — that  he  should  be  condemned  to  the  prison 
of  the  Inquisition  during  pleasure, — and  that,  during 
the  three  following  years,  he  should  recite  once  a 
week  the  seven  penitential  psalms. 

This  sentence  was  subscribed  by  seven  cardinals ; 
and  on  the  22d  June,  1633,  Galileo  signed  an  abjura- 
tion humiliating  to  himself  and  degrading  to  philoso- 


GALILEO.  133 


134  SIR   ISAAC   NEWTON. 

January,  1615,  he  defends  the  Copernican  system 
with  much  boldness  and  ingenuity;  he  reconciles 
the  various  passages  of  Scripture  with  the  new  doc- 
trine, and  he  expresses  the  hope  that  such  an  attempt, 
now  made  for  the  first  time,  will  prove  agreeable  to 
philosophers,  but  particularly  to  those  very  learned 
men,  Galileo  Galilei,  John  Kepler,  and  all  the  mem- 
bers of  the  Lyncean  Academy,  who,  he  believes, 
entertain  the  same  opinion.  This  remarkable  pro- 
duction, written  from  the  convent  of  the  Carmelites 
at  Naples,  is  dedicated  to  the  very  Reverend  Sebas- 
tian Fantoni,  general  of  the  order  of  Carmelites,  and 
was  published  at  Florence,  with  the  sanction  of  the 
ecclesiastical  authorities,  in  1630 ;  three  years  before 
the  second  persecution  of  Galileo. 

It  would  be  interesting  to  know  the  state  of  public 
feeling  in  Italy  when  Galileo  was  doomed  to  the 
prisons  of  the  Inquisition.  No  appeal  seems  to  have 
been  made  against  so  cruel  a  sentence  ;  and  neither 
in  remonstrance  nor  in  derision  does  an  individual 
voice  seem  to  have  been  raised.  The  master  spirits 
of  the  age  looked  with  sullen  indifference  on  the 
persecution  of  exalted  genius ;  and  Galileo  lay  in 
chains,  deserted  and  unpitied.  This  unrebuked  tri- 
umph of  his  enemies  was  perhaps  favourable  to  the 
object  of  their  vengeance.  Resistance  might  have 
heightened  the  rigour  of  a  sentence,  which  submis- 
sion seems  to  have  alleviated.  The  interference 
of  some  eminent  individuals  of  Rome,  among  whom 
we  have  no  doubt  that  the  Grand-duke  of  Tuscany 
was  the  most  influential,  induced  Pope  Urban  VIII., 
not  only  to  shorten  the  period,  but  to  soften  the 
rigour  of  Galileo's  imprisonment.  From  the  dun- 
geon of  the  Inquisition,  where  he  had  remained  only 
foui  days,  he  was  transported  to  the  ambassador's 
palace  in  the  Garden  de  Medici  at  Rome ;  and  when 
his  health  had  begun  to  suifer,  he  was  permitted  to 
leave  the  metropolis ;  and  would  have  been  allowed 
to  return  to  Florence,  but  as  the  plague  raged  in 


GALILEO.  135 

that  city,  he  was  sent,  in  July,  1633,  to  the  archi- 
episcopal  palace  of  Sienna,  the  residence  of  the  Arch- 
bishop Piccolimini,  where  he  carried  on  and  com- 
pleted his  valuable  investigations  respecting  the 
resistance  of  solids.  Here  he  continued  five  months, 
when,  in  consequence  of  the  disappearance  of  the 
plague  at  Florence,  he  was  allowed  to  retire  to  his 
villa  at  Bellosguardo,  and  afterward  to  that  of  Ar- 
cetri  in  the  vicinity  of  Florence. 

Though  Galileo  was  now,  to  a  certain  degree, 
liberated  from  the  power  of  man,  yet  the  afflicting 
dispensations  of  Providence  began  to  fall  thickly 
around  him.  No  sooner  had  he  returned  to  Arcetri, 
than  his  favourite  daughter,  Maria,  was  seized  with 
a  dangerous  illness,  which  soon  terminated  in  her 
death.  He  was  himself  attacked  with  hernia,  pal- 
pitation of  the  heart,  loss  of  appetite,  and  the  most 
oppressive  melancholy;  and  though  he  solicited 
permission  to  repair  to  Florence  for  medical  assist- 
ance, yet  this  deed  of  mercy  was  denied  him.  In 
1638,  however,  the  pope  permitted  him  to  pay  a  visit 
to  Florence,  and  his  friend,  Father  Castelli,  was 
allowed  to  visit  him  in  the  company  of  an  officer  of 
the  Inquisition.  But  this  indulgence  was  soon  with- 
drawn, and  at  the  end  of  a  few  months  he  was  re- 
manded to  Arcetri.  The  sight  of  his  right  eye  had 
begun  to  fail  in  1636,  from  an  opacity  of  the  cornea. 
In  1637  his  left  eye  was  attacked  with  the  same 
complaint ;  so  that  in  a  few  months  he  was  affected 
with  total  and  incurable  blindness.  Before  this  ca- 
lamity had  supervened,  he  had  noticed  the  curious 
phenomenon  of  the  moon's  libration,  in  consequence 
of  which,  parts  of  her  visible  disk  that  are  exposed 
to  view  at  one  time  are  withdrawn  at  another.  He 
succeeded  in  explaining  two  of  the  causes  of  this 
curious  phenomenon,  viz.  the  different  distances  of 
the  observer  from  the  line  joining  the  centre  of  .the 
earth  and  the  moon,  which  produces  the  diurnal 
libration,  and  the  unequal  motion  of  the  moon  in  her 


136 


SIR   ISAAC    NEWTON. 


orbit,  which  produces  the  libration  in  longitude.  It 
was  left,  however,  to  Hevelius  to  discover  the  libra- 
tion in  latitude,  which  arises  from  the  inclination  of 
her  axis  being  a  little  less  than  a  right  angle  to  the 
ecliptic ;  and  to  Lagrange  to  discover  the  spheroidal 
libration,  or  that  which  arises  from  the  action  of  the 
earth  upon  the  lunar  spheroid. 

The  sorrows  with  which  Galileo  was  now  beset, 
seemed  to  have  disarmed  the  severity  of  the  Inqui- 
sition. He  was  freely  permitted  to  enjoy  the  society 
of  his  friends,  who  now  thronged  around  him  to 
express  their  respect  and  their  sympathy.  The 
Grand-duke  of  Tuscany  was  his  frequent  visiter, 
and  Gassendi,  Deodati,  and  our  countryman  Milton 
went  to  Italy  for  the  purpose  of  visiting  him.  He 
entertained  his  friends  with  the  warmest  hospitality, 
and  though  simple  and  abstemious  in  his  diet,  yet  he 
was  fond  of  good  wine,  and*  seems  even  in  his  last 
days  to  have  paid  particular  attention  to  the  excel- 
lence of  his  cellar. 

Although  Galileo  had  nearly  lost  his  hearing  as 
well  as  his  sight,  yet  his  intellectual  faculties  were 
unimpaired;  and  while  his  mind  was  occupied  in 
considering  the  force  of  percussion,  he  was  seized 
with  fever  and  palpitation  of  the  heart,  which,  after 
two  months'  illness,  terminated  his  life  on  the  8th 
of  January,  1642. 

Among  the  predecessors  of  Newton  in  astro- 
nomical research  we  must  not  omit  the  names  of 
Bouillaud  (Bullialdus),  Borelli,  and  Dr.  Hooke. 
Ismael  Bouillaud,  a  native  of  Laon  in  France,  and 
the  author  of  several  valuable  astronomical  works, 
has  derived  more  reputation  from  a  single  -sentence 
in  his  Astronomica  Philolaica,  published  in  1645,  than 
from  all  the  rest  of  his  labours.  He  was  not  a  be- 
liever in  the  doctrine  of  attraction,  which,  as  we 
have  already  seen,  had  been  broached  by  Copernicus, 
and  discovered  by  Kepler ;  but  in  speaking  of  that 
power  as  the  cause  of  the  planetary  motions,  he 


BORELLI HOOKE.  137 

remarks,  "that  if  attraction  existed,  it  would  de- 
crease as  the  square  of  the  distance."  The  influ- 
ence of  gravity  was  still  more  distinctly  developed 
by  Borelli,  a  Neapolitan  philosopher,  who  published 
h  1666  a  work  on  Jupiter's  satellites.*  In  this  work 
he  maintains,  that  all  the  planets  perform  their  mo- 
tions round  the  sun  according-  to  a  general  law ;  that 
the  satellites  of  Jupiter  and  of  Saturn  move  round 
their  primary  planets  in  the  same  manner  as  the 
moon  does  round  the  earth,  and  that  they  all  re- 
volve round  the  sun,  which  is  the  only  source  of 
any  virtue,  and  that  this  virtue  attaches  them,  and 
unites  them  so  that  they  cannot  recede  from  their 
centre  of  action,  f 

Our  countryman  Dr.  Robert  Hooke  seems  to 
have  devoted  much  of  his  attention  to  the  cause  of 
the  planetary  motions.  On  the  21st  March,  1666, 
he  read  to  the  Royal  Society  an  account  of  a  series 
of  experiments  for  determining  if  bodies  experience 
any  variation  in  their  weight  at  different  distances 
from  the  centre  of  the  earth.  His  experiments,  as 
Hooke  himself  saw,  were  by  no  means  satisfactory, 
and  hence  he  was  led  to  the  ingenious  idea  of 
measuring  the  force  of  gravity  by  observing,  at  dif- 
ferent altitudes,  the  rate  of  a  pendulum  clock. 
About  two  months  afterward,  he  exhibited  to  the 
Society  an  approximate  representation  of  the  forces 
which  retain  the  planets  in  their  orbits,  in  the  paths 
described  by  a  circular  pendulum  impelled  with  dif- 

*  TheorictB  Medicearum  planetarum  ex  causis  physicis  deducts 
Flor  1666,  4to. 

t  M.  Delambre  maintains  that  these  views  of  Borelli  are  only  those  of 
Kepler  slightly  modified.  Newton  and  Huygens  have  attached  to  them 
a  greater  value.  The  last  of  these  philosophers  remarks,  "  Refert  Plu- 
tarchus,  fuisse  jam  olim  qui  putaret  ideo  manere  lunam  in  orbe  suo,  quod 
vis  recedendi  a  terra,  ob  motum  circularem,  inhiberetur  pan  vi  gravi- 
tatis,  qua  ad  terram  accedere  conaretur.  Idemque  aevo  nostro,  non  de 
lunatantum  sed  et  planetis  ceteris  statuit  Alphonsus  Borellus,  utnempe 
primariis  eorum  gravitas  esset  solem  versus ;  lunis  vero  ad  terram, 
Jovemac  Saturnum  quos  comitantiir."— Huygen,  Cosmotheor,  lib  »».; 
Opera,  t.  ii.  p.  720. 

M2 


138  SIR   ISAAC   NEWTON. 

ferent  degrees  of  force  ;  but  though  this  experiment 
illustrated  the  production  of  a  curvilineal  motion,  by 
combining  a  tangential  force  with  a  central  power 
of  attraction,  yet  it  was  only  an  illustration,  and 
could  not  lead  to  the  true  cause  of  the  planetary  mo- 
tions. At  a  later  period,  however,  viz.  in  1674, 
Hooke  resumed  the  subject  in  a  dissertation  entitled 
"  An  Attempt  to  prove  the  Motion  of  the  Earth  from 
Observation,"  which  contains  the  following  remark- 
able observations  upon  gravity: — 

"  I  shall  hereafter  explain  a  system  of  the  world 
differing  in  many  particulars  from  any  yet  known, 
answering  in  all  things  to  the  common  rules  of  me- 
chanical motions.  This  depends  upon  three  suppo- 
sitions:— first,  that  all  celestial  bodies  whatsoever 
have  an  attraction  or  gravitating  power  towards 
their  own  centres,  whereby  they  attract,  not  only 
their  own  parts,  and  keep  them  from  flying  from 
them,  as  we  may  observe  the  earth  to  do,  but  that 
they  also  do  attract  all  the  other  celestial  bodies 
that  are  within  the  sphere  of  their  activity,  and  con- 
sequently, that  not  only  the  sun  and  moon  have  an 
influence  upon  the  body  and  motion  of  the  earth, 
and  the  earth  upon  them,  but  that  Mercury,  Venus, 
Mars,  Jupiter,  and  Saturn,  also,  by  their  attractive 
powers,  have  a  considerable  influence  upon  its  mo- 
tion, as  in  the  same  manner  the  corresponding  at- 
tractive power  of  the  earth  hath  a  considerable  in- 
fluence upon  every  one  of  their  motions  also.  The 
second  supposition  is  this,  that  all  bodies  what- 
soever that  are  put  into  a  direct  and  simple  motion 
will  so  continue  to  move  forward  in  a  straight  line, 
till  they  are,  by  some  other  effectual  powers,  de- 
flected, and  sent  into  a  motion  describing  a  circle, 
ellipsis,  or  some  other  more  compounded  curve  line. 
The  third  supposition  is,  that  those  attractive  pow- 
eis  are  so  much  the  more  powerful  in  operating  by 
how  much  the  nearer  the  body  wrought  upon  is  to  their 
own  centres.  Now9  what  these  several  degrees  are  1 


LAW   OF   GRAVITY.  130 

have  not  yet  'experimentally  verified ;  but  it  is  a  notion 
which,  if  ftey  prosecute^  as  it  ought  to  be,  will 
mightily  assist  the  astronomers  to  reduce  all  the 
celestial  motions  to  a  certain  rule,  which  I  doubt 
will  never  be  done  without  it.  He  that  understands 
the  nature  of  the  circular  pendulum  and  circular 
motion  will  easily  understand  the  whole  of  this 
principle,  and  will  know  where  to  find  directions  in 
nature  for  the  true  stating  thereof.  This  I  only 
hint  at  present  to  such  as  have  ability  and  opportu- 
nity of  prosecuting  this  inquiry,  and  are  not  wanting 
of  industry  for  observing  and  calculating,  wishing 
heartily  such  may  be  found,  having  myself  many 
other  things  in  hand,  which  I  would  first  complete, 
and  therefore  cannot  so  well  attend  it.  But  this  I 
do  not  promise  the  undertaker,  that  he  will  find  all 
the  great  motions  of  the  world  to  be  influenced  by 
this  principle,  and  that  the  true  understanding 
thereof  will  be  the  true  perfection  of  astronomy." 
This  passage,  which  has  been  considered  as  a  re- 
markable one  by  the  philosophers  of  every  country, 
has,  we  think,  been  misapprehended  by  M.  Delam- 
bre,  when  he  asserts  that  every  thing  which  it  con- 
tains "  is  to  be  found  expressly  in  Kepler."* 

*  Hist,  de  VA&tronomie  aux  Dioc-huitieme  Sttcle,  p.  9. 


140  SIR   ISAAC   NEWTON. 


CHAPTER  XL 

The  first  Idea  of  Gravity  occurs  to  Newton  in  1666 — His  first  Specu- 
lations upon  it—Interrupted  by  his  Optical  Experiments— He  re- 
sumes the  Subject  in  consequence  of  a  Discussion  with  Dr.  Heoke — 
He. discovers  the  true  Law  of  Gravity  and  the  Cause  oftfie  Planetary 
Motions — Dr.  Halley  urges  him  to  publish  his  Principia — His  Prin- 
ciples of  Natural  Philosophy— Proceedings  of  the  Royal  Society  on 
this  Subject — The  Principia  appears  in  16S7 — General  Account  of  it, 
and  of  the  Discoveries  it  contains — They  meet  with  great  Opposition, 
owing  to  the  Prevalence  of  the  Cartesian  System — Account  of  the  Re- 
ception and  Progress  of  the  Newtonian  Philosophy  in  foreign  Coun- 
tries— Account  of  its  Progress  and  Establishment  in  England. 

SUCH  is  a  brief  sketch  of  the  labours  and  lives  of 
those  illustrious  men  who  prepared  the  science  of 
astronomy  for  the  application  of  Newton's  genius. 
Copernicus  had  determined  the  arrangement  and 
general  movements  of  the  planetary  bodies :  Kepler 
had  proved  that  they  moved  in  elliptical  orbits ; 
that  their  radii  vectores  described  arcs  proportional 
to  the  times;  and  that  their  periodic  times  wer 
related  to  their  distances.  Galileo  had  added  to  the 
universe  a  whole  system  of  secondary  planets ;  and 
several  astronomers  had  distinctly  referred  the  mo- 
tion of  the  heavenly  bodies  to  the  power  of  attraction. 

In  the  year  1666,  when  the  plague  had  driven 
Newton  from  Cambridge,  he  was  sitting  alone  in 
the  garden  at  Woolsthorpe,  and  reflecting  on  the 
nature  of  gravity, — that  remarkable  power  which 
causes  all  bodies  to  descend  'towards  the  centre  of 
the  earth.  As  this  power  is  not  found  to  suffer  any 
sensible  diminution  at  the  greatest  distance  from 
the  earth's  centre  to  which  we  can  reach,  being  as 
powerful  at  the  tops  of  the  highest  mountains  as  at 
the  bottom  of  the  deepest  mines,  he  conceived  it 
highly  probable,  that  it  must  extend  much  farther 
than  was  usually  supposed.  No  sooner  had  this 


NEWTON'S  IDEA  OF  GRAVITY.  lit 

conjecture  occurred  to  his  mind,  than  he  con- 
le'red  what  would  be  the  effect  of  its  extending  as 
far  as  the  moon.  That  her  motion  must  be  influ- 
enced by  such  a  power  he  did  not  for  a  moment 
doubt ;  and  a  little  reflection  convinced  him  that  it 
might  be  sufficient  for  retaining  that  luminary  in  her 
orbit  round  the  earth.  Though  the  force  of  gravity 
suffers  no  sensible  diminution  at  those  small  dis- 
tances from  the  earth's  centre  at  which  we  can 
place  ourselves,  yet  he  thought  it  very  possible, 
that,  at  the  distance  of  the  moon,  it  might,  differ 
much  in  strength  from  what  it  is  on  the  earth.  In 
order  to  form  some  estimate  of  the  degree  of  its 
diminution,  he  considered  that,  if  the  moon  be  re- 
tained in  her  orbit  by  the  force  of  gravity,  the  pri- 
mary planets  must  also  be  carried  round  the  sun  by 
the  same  power ;  and  by  comparing  the  periods  of 
the  different  planets  with  their  distances  from  the 
sun,  he  found,  that  if  they  were  retained  in  their 
orbits  by  any  power  like  gravity,  its  force  must  de- 
crease in  the  duplicate  proportion,*  or  as  the  squares 
of  their  distances  from  the  sun.  In  drawing  this 
conclusion,  he  supposed  the  planets  to  move  in  or- 
bits perfectly  circular,  and  having  the  sun  in  their 
centre.  Having  thus  obtained  the  law  of  the  force 
by  which  the  planets  were  drawn  to  the  sun,  his 
next  object  was  to  ascertain  if  such  a  force,  ema- 
nating from  the  earth  and  directed  to  the  moon,  was 
sufficient,  when  diminished  in  the  duplicate  ratio  of 
the  distance,  to  retain  her  in  her  orbit.  In  perform- 
ing this  calculation,  it  was  necessary  to  compare 
the  space  through  which  heavy  bodies  fall  in  a  second 
at  a  given  distance  from  the  centre  of  the  earth,  viz. 
at  its  surface,  with  the  space  through  which  the 
moon,  as  it  were,  falls  to  the  earth  in  a  second  of 
time  while  revolving  in  a  circular  orbit.  Being  at 

*  "  But  for  the  duplicate  proportion,  I  gathered  it  from  Kepler's  theo- 
rem about  twenty  years  ago."— Newton's  Letter  to  Halley,  July  14, 1686. 


142  SIR   ISAAC   NEWTON. 

a  distance  from  books  when  he  made  this  compu- 
tation, he  adopted  the  common  estimate  of  the  earth's 
diameter  then  in  use  among  geographers  and  navi- 
gators, and  supposed  that  each  degree  of  latitude 
contained  sixty  English  miles.  In  this  way  he 
found  that  the  force  which  retains  the  moon  in  her 
orbit,  as  deduced  from  the  force  which  occasions  the 
fall  of  heavy  bodies  to  the  earth's  surface,  was  one- 
sixth  greater  than  that  which  is  actually  observed  in 
her  circular  orbit.  This  difference  threw  a  doubt 
upon  all  his  speculations ;  but,  unwilling  to  abandon 
what  seemed  to  be  otherwise  so  plausible,  he  endeav- 
oured to  account  for  the  difference  of  the  two  forces, 
by  supposing  that  some  other  cause*  must  have  been 
united  with  the  force  of  gravity  in  producing  so 
great  a  velocity  of  the  moon  in  her  circular  orbit. 
As  this  new  cause,  however,  was  beyond  the  reach 
of  observation,  he  discontinued  all  further  inquiries 
into  the  subject,  and  concealed  from  his  friends  the 
speculations  in  which  he  had  been  employed. 
^  After  his  return  to  Cambridge  in  1666,  his  atten- 
tion was  occupied  with  those  optical  discoveries  of 
which  we  have  given  an  account  in  a  preceding 
chapter ;  but  he  had  no  sooner  brought  them  to  a 
close  than  his  mind  reverted  to  the  great  subject  of 
the  planetary  motions.  Upon  the  death  of  Olden- 
burg in  August,  1678,  Dr.  Hooke  was  appointed 
secretary  to  the  Royal  Society ;  and  as  this  learned 
body  had  requested  the  opinion  of  Newton  about  a 
system  of  physical  astronomy,  he  addressed  a  letter 
to  Dr.  Hooke  on  the  28th  November,  1679.  In  this 
letter  he  proposed  a  direct  experiment  for  verifying 
the  motion  of  the  earth,  viz.  by  observing  whether 
or  not  bodies  that  fall  from  a  considerable  height 
descend  in  a  vertical  direction,  for  if  the  earth  were 
at  rest  the  body  would  describe  exactly  a  vertical 

*  Whiston  asserts  that  this  cause  was  supposed  by  Newton  to  be 
something  analogous  to  the  vortices  of  Descartes.— See  Whiston's  Me- 
moirs  of  himself,  p.  231. 


LAW    OF    GRAVITY.  143 

line,  whereas  if  it  revolved  round  its  axis,  the  falling 
body  must  deviate  from  the  vertical  line  towards  the 
east.  The  Royal  Society  attached  great  value  to  * 
the  idea  thus  casually  suggested,  and  Dr.  Hooke  was 
appointed  to  put  it  to  the  test  of  experiment.  Being 
thus  led  to  consider  the  subject  more  attentively,  he 
wrote  to  Newton,  that  wherever  the  direction  of 
gravity  was  oblique  to  the  axis  on  which  the  earth 
revolved,  that  is,  in  every  part  of  the  earth  ex- 
cept the  equator,  falling  bodies  should  approach 
to  the  equator,  and  the  deviation  from  the  ver- 
tical, in  place  of  being  exactly  to  the  east,  as 
Newton  maintained,  should  be  to  the  south-east  of  ~ 
the  point  from  which  the  body  began  to  move. 
Newton  acknowledged  that  this  conclusion  was  cor- 
rect in  theory,  and  Dr.  Hooke  is  said  to  have  given 
an  experimental  demonstration  of  it  before  the  Royal 
Society  in  December,  1679.*  Newton  had  errone-^" 
ously  concluded  that  the  path  of  the  falling  body 
would  be  a  spiral;  but  Dr.  Hooke,  on  the  same 
occasion  on  which  he  made  the  preceding  experi- 
ment, read  a  paper  to  the  Society,  in  which  he  proved 
that  the  path  of  the  body  would  be  an  eccentric 
ellipse  in  vacuo,  and  an  ellipti-spiral,  if  the  body 
moved  in  a  resisting  medium-! 

This  correction  of  Newton's  error,  and  the  dis- 
covery that  a  projectile  would  move  in  an  elliptical 
orbit  when  under  the  influence  of  a  force  varying  in 
the  inverse  ratio  of  the  square  of  the  distance,  led 
Newton,  as  he  himself  informs  us  in  his  letter  to 
Halley,J  to  discover  "  the  theorem  by  which  he  af- 
terward examined  the  ellipsis,"  and  to  demonstrate 
the  celebrated  proposition,  that  a  planet  acted  upon 
by  an  attractive  force  varying  inversely  as  the 
squares  of  the  distances  will  describe  an  elliptical 
orbit,  in  one  of  whose  foci  the  attractive  force  re- 
sides. 

*  Waller's  Life  of  Hooke,  p.  22. 
J  July  27, 1686,  Biog.  Brit.  p.  2662. 


144  SIR   ISAAC   NEWTON. 

But  though  Newton  had  thus  discovered  the  true 
cause  of  all  the  celestial  motions,  he  did  not  yet 
possess  any  evidence  that  such  a  force  actually  re- 
sided in  the  sun  and  planets.  The  failure  of  his 
former  attempt  to  identify  the  law  of  falling  bodies 
at  the  earth's  surface  with  that  which  guided  the 
moon  in  her  orbit  threw  a  doubt  over  all  his  specu- 
lations, and  prevented  him  from  giving  any  account 
of  them  to  the  public. 

*  An  accident,  however,  of  a  very  interesting  nature 
induced  him  to  resume  his  former  inquiries,  and 
enabled  him  to  bring  them  to  a  close.  In  June, 
1682,  when  he  was  attending  a  meeting  of  the  Royal 
Society  of  London,  the  measurement  of  a  degree  of 
the  meridian,  executed  by  M.  Picardin  1679,  became 
the  subject  of  conversation.  Newton  took  a  memo- 
randum of  the  result  obtained  by  the  French  astron- 
omer, and  having  deduced  from  it  the  diameter  of  the 
earth,  he  immediately  resumed  his  calculation  of 
1665,  and  began  to  repeat  it  with  these  new  data. 
In  the  progress  of  the  calculation  he  saw  that  the 
result  which  he  had  formerly  expected  was  likely  to 
be  produced,  and  he  was  thrown  into  such  a  state  of 
nervous  irritability  that  he  was  unable  to  carry  on 
the  calculation.  In  this  state  of  mind  he  intrusted 
it  to  one  of  his  friends,  and  he  had  the  high  satis- 
faction of  finding  his  former  views  amply  realized. 
The  force  of  gravity  which  regulated  the  fall  of 
bodies  at  the  earth's  surface,  when  diminished  as 
the  square  of  the  moon's  distance  from  the  earth, 
was  found  to  be  almost  exactly  equal  to  the  centri- 
L,  fugal  force  of  the  moon  as  deduced  from  her  observed 
distance  and  velocity. 

The  influence  of  such  a  result  upon  such  a  mind 
maybe  more  easily  conceived  than  described.  The 
whole  material  universe  was  spread  out  before  him ; 
— the  sun  with  all  his  attending  planets ; — the  planets 
with  all  their  satellites; — the  comets  wheeling  in 
every  direction  in  their  eccentric  orbits ; — and  the 


PLANETARY   MOTIONS.  145 

systems  of  the  fixed  stars  stretching  to  the  remotest 
limits  of  space.  All  the  varied  and  complicated 
movements  of  the  heavens,  in  short,  must  have  been 
at  once  presented  to  his  mind,  as  the  necessary  result 
of  that  law  which  he  had  established  in  reference  to 
the  earth  and  the  moon. 

After  extending  this  law  to  the  other  bodies  of 
;he  system,  he  composed  a  series  of  propositions 
on  the  motion  of  the  primary  planets  about  the  siin^ 
which  were  sent  to  London  about  the  end  of  1683, 
and  were  soon  afterward  communicated  to  tfre 
[loj'al  Society.* 

About  this  period  other  philosophers  had  been 
occupied  with  the  same  subject.  Sir  Christopher 
Wren  had  many  years  before  endeavoured  to  ex- 
plain the  planetary  motions  "by  the  composition 
of  a  descent  towards  the  sun,  and  an  impressed 
motion ;  but  he  at  length  gave  it  over,  not  finding 
he  means  of  doing  it."  In  January,  1683-4,  Dr. 
Galley  had  concluded,  from  Kepler's  Law  of  the 
Periods  and  Distances,  that  the  centripetal  force  de- 
Teased  in  the  reciprocal  proportion  of  the  squares 
of  the  distances,  and  having  one  day  met  Sir  Chris- 
;opher  Wren  and  Dr.  Hooke,  the  latter  affirmed 
,hat  he  had  demonstrated  upon  that  principle  all 
;he  laws  of  the  celestial  motions.  Dr.  Halley  con- 
ressed  that  his  attempts  were  unsuccessful,  and 
Sir  Christopher,  in  order  to  encourage  the  inquiry, 
offered  to  present  a  book  of  forty  shillings'  value  to 
either  of  the  two  philosophers  who  should,  in  the 
space  of  two  months,  bring  him  a  convincing  de- 
monstration of  it.  Hooke  persisted  in  the  decla-  * 
ration  that  he  possessed  the  method,  but  avowed  it 
to  be  his  intention  to  conceal  it  for  some  time.  He 
promised,  however,  to  show  it  to  Sir  Christopher ; 
but  there  is  every  reason  to  believe  that  this  prom- 
ise was  never  fulfilled. 

In  August,  1684,,  Dr.  Halley  went  to  Cambridge 

*  Commercium  Epistolicumt  No.  7 


'146  SIR   ISAAC   NEWTON. 

for  the  express  purpose  of  consulting  Newton  on 
this  interesting  subject.  Newton  assured  him  that 
he  had  brought  this  demonstration  to  perfection, 
and  promised  him  a  copy  of  it.  This  copy  was  re- 
ceived in  November  by  the  doctor,  who  made  a 
second  visit  to  Cambridge,  in  order  to  induce  its 
author  to  have  it  inserted  in  the  register  book  of 
the  society.  On  the  10th  of  December,  Dr.  Halley 
announced  to  the  society,  that  he  had  seen  at  Cam- 
bridge Mr.  Newton's  treatise  De  Motu  Corporum, 
which  he  had  promised  to  send  to  the  society  to  be 
entered  upon  their  register ;  and  Dr.  Halley  was  de- 
sired to  unite  with  Mr.  Paget,  master  of  the  mathe- 
matical school  in  Christ's  Hospital,  in  reminding 
Mr.  Newton  of  his  promise  "  for  securing  the  inven- 
tion to  himself  till  such  time  as  he  can  be  at  leisure 
to  publish  it."  On  the  25th  February  Mr.  Aston, 
the  secretary,  communicated  a  letter  from  Mr. 
Newton,  in  which  he  expressed  his  willingness  "  to 
enter  in  the  register  his  notions  about  motion,  and 
his  intentions  to  fit  them  suddenly  for  the  press." 
The  progress  of  his  work  was,  however,  interrupted 
by  a  visit  of  five  or  six  weeks  which  he  made  in 
Lincolnshire ;  but  he  proceeded  with  such  diligence 
on  his  return,  that  he  was  able  to  transmit  the  manu- 
script to  London  before  the  end  of  April.  This 
manuscript,  entitled  Philosophic  Naturalis  Principia 
Mathematica^  and  dedicated  to  the  society,  was  pre- 
sented by  Dr.  Vincent  on  the  28th  April,  1686,  when 
Sir  John  Hoskins,  the  vice-president,  and  the  par- 
ticular friend  of  Dr.  Hooke,  was  in  the  chair.  Dr. 
Vincent  passed  a  just  encomium  on  the  novelty  and 
dignity  of  the  subject ;  and  another  member  added, 
that  "  Mr.  Newton  had  carried  the  thing  so  far,  that 
there  was  no  more  to  be  added."  To  these  remarks 
the  vice-president  replied,  that  the  method  "  was  so 
much  the  more  to  be  prized  as  it  was  both  invented 
and  perfected  at  the  same  time."  Dr.  Hooke  took 
offence  at  these  remarks,  and  blamed  Sir  John  for 


PRINCIPIA.  147 

ipt  having  mentioned  "  what  he  had  discovered  to 
lim ;"  but  the  vice-president  did  not  seem  to  recol- 
ect  any  such  communication,  and  the  consequence 
)f  this  discussion  was,  that  "  these  two,  who  till 
hen  were  the  most  inseparable  cronies,  have  since 
scarcely  seen  one  another,  and  are  utterly  fallen 
>ut."  After  the  breaking  up  of  the  meeting,  the 
ociety  adjourned  to  the  coffee-house,  where  Dr. 
Hooke  stated  that  he  not  only  had  made  the  same 
iiscovery,  but  had  given  the  first  hint  of  it  to  Newton. 
An  account  of  these  proceedings  was  communi- 
ated  to  Newton  through  two  different  channels, 
n  a  letter  dated  May  22d,  Dr.  Halley  wrote  to  him 
that  Mr.  Hooke  has  some  pretensions  upon  the 
nvention  of  the  rule  of  the  decrease  of  gravity  be- 
ig  reciprocally  as  the  squares  of  the  distances  from 
le  centre.  He  says  you  had  the  notion  from  him, 
lough  he  owns  the  demonstration  of  the  curves 
enerated  thereby  to  be  wholly  your  own.  How 
nuch  of  this  is  so  you  know  best,  as  likewise  what 
ou  have  to  do  in  this  matter.  Only  Mr.  Hooke 
eems  to  expect  you  would  make  some  mention  of 
im  in  the  preface,  which  it  is  possible  you  may 
ee  reason  to  prefix." 

'This  communication   from  Dr.  Halley  induced 

ur  author,  on  the  20th  June,  to  address  a  long 

itter  to  him,  in  which  he  gives  a  minute  and  able 

Mutation  of  Hooke's  claims ;  but  before  this  letter 

as  despatched,  another  correspondent,  who  had 

eceived  his  information  from  one  of  the  members 

lat  were  present,  informed  Newton  "  that  Hooke 

nade  a  great  stir,  pretending  that  he  had  all  from 

im,  and  desiring  they  would  see  that  he  had  justice 

one  him."    This  fresh  charge  seems  to  have  ruf- 

ed  the  tranquillity  of  Newton ;  and  he  accordingly 

idded  an  angry  and  satirical  postscript,  in  which  he 

treats  Hooke  with  little  ceremony,  and  goes  so  far 

as  to  conjecture  that  Hooke  might  have  acquired 

his  knowledge  of  the  law  from  a  letter  of  his  own 


148  SIR   ISAAC   NEWTON. 

to  Huygens,  directed  to  Oldenburg,  and  dated  Janu- 
ary 14th,  1672-3.  "My  letter  to  Hugenius  was 
directed  to  Mr.  Oldenburg,  who  used  to  keep  the 
originals.  His  papers  came  into  Mr.  Hooke's  pos- 
session. Mr.  Hooke,  knowing  my  hand,  might  have 
the  curiosity  to  look  into  that  letter,  and  there  take 
the  notion  of  comparing  the  forces  of  the  planets 
arising  from  their  circular  motion ;  and  so  what  he 
wrote  to  me  afterward  about  the  rate  of  gravity 
might  be  nothing  but  the  fruit  of  my  own  garden." 

In  replying  to  this  letter,  Dr.  Halley  assured  him 
that  Hooke's  "manner  of  claiming  the  discovery 
had  been  represented  to  him  in  worse  colours  than 
it  ought,  and  that  he  neither  made  public  application 
to  the  society  for  justice,  nor  pretended  that  you 
had  all  from  him."  The  effect  of  this  assurance 
was  to  make  Newton  regret  that  he  had  written  the 
angry  postscript  to  his  letter;  and  in  replying  to 
Halley  on  the  14th  July,  1686,  he  not  only  expresses 
his  regret,  but  recounts  the  different  new  ideas 
which  he  had  acquired  from  Hooke's  correspon- 
dence, and  suggests  it  as  the  best  method  "  of  com- 
promising the  present  dispute,"  to  add  a  scholium, 
in  which  Wren,  Hooke,  and  Halley  are  acknowledged 
to  have  independently  deduced  the  law  of  gravity 
from  the  second  law  of  Kepler.* 

At  the  meeting  of  the  28th  April,  at  which  the 
manuscript  of  the  Principia  was  presented  to  the 
Royal  Society,  it  was  agreed  that  the  printing  of  it 
should  be  referred  to  the  council ;  that  a  letter  of 
thanks  should  be  written  to  its  author;  and  at  a 
meeting  of  the  council  on  the  19th  May,  it  was 
resolved  that  the  MSS.  should  be  printed  at  the 
society's  expense,  and  that  Dr.  Halley  should  super- 
intend it  while  going  through  the  press.  These 
resolutions  were  communicated  by  Dr.  Halley  in  a 
letter  dated  the  22d  May ;  and  in  Newton's  replv  on 
the  20th  June  already  mentioned,  he  makes  the  fol  • 

*  This  Scholium  is  added  to  Prop.  iv.  lib.  i.  coroll  6. 


PRINCIPIA.  149 

towing  observations :   "  The  proof  you  sent  me  I 
like  very  well.     I  designed  the  whole  to  consist  of 
three  books ;  the  second  was  finished  last  summer, 
being  short,  and  only  wants  transcribing,  and  draw- 
I  trig  the  cuts  fairly.     Some  new  propositions  I  have 
bince  thought  on,  which  I  can  as  well  let  alone. 
[The  third  wants  the  theory  of  comets.    In  autumn 
|  last  I  spent  two  months  in  calculation  to  no  purpose 
I  for  want  of  a  good  method,  which  made  me  after- 
[ward  return  to  the  first  book,  and  enlarge  it  with 
[diverse  propositions,  some  relating  to  comets,  others 
|  to  other  things  found  out  last  winter.    The  third  I 
(now  design  to  suppress.    Philosophy  is  such  an  im- 
pertinently litigious  lady,  that  a  man  had  as  good  be 
I  engaged  in  lawsuits  as  have  to  do  with  her.     I 
found  it  so  formerly,  and  now  I  can  no  sooner  come 
near  her  again  but  she  gives  me  warning.    The  first 
two  books  without  the  third  will  not  so  well  bear 
the  title  of  Philosophise,  Naturalis  Principia  Mathe- 
\matica  ;  and  therefore  I  had  altered  it  to  this,  De 
\  Motu  Corporum  Libri  duo.     But  after  second  thoughts 
il  retain  the  former  title.     It  will  help  the  sale  of  the 
!  book,  which  I  ought  not  to  diminish  now  'tis  yours." 
In  replying  to  this  letter  on  the  29th  June,  Dr. 
Halley  regrets  that  our  author's  tranquillity  should 
have  been  thus  disturbed  by  envious  rivals;   and 
implores  him  in  the  name  of  the  society  not  to 
suppress  the  third  book.     "  I  must  again  beg  you," 
says  he,  "  not  to  let  your  resentments  run  so  high 
as  to  deprive  us  of  your  third  book,  wherein  your 
applications  of  your  mathematical  doctrine  to  the 
theory  of  comets,  and  several  curious  experiments, 
which,  as  I  guess  by  what  you  write  ought  to  com- 
pose it,  will  undoubtedly  render  it  acceptable  to 
those  who  will  call  themselves  philosophers  without 
mathematics,  which  are  much  the  greater  number.'* 
To  these  solicitations  Newton  seems  to  have 
readily  yielded.    His  second  book  was  sent  to  the 
society,  and  presented  on  the  2d  March,  1686-7. 


150  SIR   ISAAC   NEWTON. 

The  third  book  was  also  transmitted,  and  presented 
on  the  6th  April,  and  the  whole  work  was  completed 
and  published  in  the  month  of  May,  1687. 

Such  is  a  brief  account  of  the  publication  of  a 
work  which  is  memorable,  not  only  in  the  annals  ofj 
one  science  or  of  one  country,  but  which  will  form 
an  epoch  in  the  history  of  the  world,  and  will  ever 
be  regarded  as  the  brightest  page  in  the  records  of 
human  reason.  We  shall  endeavour  to  convey  to 
the  reader  some  idea  of  its  contents,  and  of  the  bril- 
liant discoveries  which  it  disseminated  over  Europe. 

The  Principia  consists  of  three  books.  The  first 
and  second,  which  occupy  three-fourths  of  the  work, 
are  entitled,  On  the  Motion  of  Bodies ;  and  the  third 
bears  the  title,  On  the  System  of  the  World.  The 
first  two  books  contain  the  mathematical  principles 
of  philosophy,  namely,  the  laws  and  conditions  of 
motions  and  forces ;  and  they  are  illustrated  with 
several  philosophical  scholia,  which  treat  of  some  ofj 
the  most  general  and'  best  established  points  in  phi- 
losophy, such  as  the  density  and  resistance  of  bodies, 
spaces  void  of  matter,  and  the  motion  of  sound  and 
light.  The  object  of  the  third  book  is  to  deduce 
from  these  principles  the  constitution  of  the  system 
of  the  world ;  and  this  book  has  been  drawn  up  in 
as  popular  a  style  as  possible,  in  order  that  it  may 
be  generally  read. 

The  great  discovery  which  characterizes  the 
Principia  is  that  of  the  principle  of  universal  gravi- 
tation, as  deduced  from  the  motion  of  the  moon, 
and  from  the  threegreat  facts  or  laws  discovered  Jby 
^Ke_pler.  This  principle  is,  that  every~~pdriicle  of 
matter  is  attracted  by,  or  gravitates  to,  every  other 
particle  of  matter,  with  a  force  inversely  proportional 
to  the  squares  of  their  distances.  From  the  first  law 
of  Kepler,  namely,  the  proportionality  of  the  areas 
to  the  times  of  their  description,  Newton  inferred 
that  the  force  which  kept  the  planet  in  its  orbit  was 
always  directed  to  the  sun;  and  from  the  second 


UNIVERSAL   GRAVITATION.  l£l 

law  of  Kepler,  that  every  planet  moves  in  an  ellipse 
i  with  the  sun  in  one  of  its  foci,  he  drew  the  still  more 
general  inference,  that  the  force  by  which  the  planet 
Inoves  round  that  focus  varies  inversely  as  the 
[square  of  its  distance  from  the  focus.  As  this  law 
:was  true  in  the  motion  of  satellites  round  their  pri- 
mary planets,  Newton  deduced  the  equality  of  gravity 
in  all  the  heavenly  bodies  towards  the  sun,  upon  the 
supposition  that  they  are  equally  distant  from  its 
centre ;  and  in  the  case  of  terrestrial  bodies,  he  sue 
needed  in  verifying  this  truth  by  numerous  and  accu 
rate  experiments. 

By  taking  a  more  general  view  of  the  subject 
Newton  demonstrated  that  a  conic  section  was  the 
only  curve  in  which  a  body  could  move  when  acted 
upon  by  a  force  varying  inversely  as  the  square  of 
he  distance ;  and  he  established  the  conditions  de- 
pending on  the  velocity  and  the  primitive  position 
of  the  body,  which  were  requisite  to  make  it  de- 
scribe a  circular,  an  elliptical,  a  parabolic,  or  a 
lyperbolic  orbit. 

Notwithstanding  the  generality  and  importance 
of  these  results,  it  still  remained  to  be  determined 
whether  the  force  resided  in  the  centres  of  the 
)lanets,  or  belonged  to  each  individual  particle  of 
which  they  were  composed.  Newton  removed  this 
incertainty  by  demonstrating,  that  if  a  spherical 
>ody  acts  upon  a  distant  body  with  a  force  varying 
as  the  distance  of  this  body  from  the  centre  of  the 
phere,  the  same  effect  will  be  produced  as  if  each 
>f  its  particles  acted  upon  the  distant  body  accord- 
ing to  the  same  law.  And  hence  it  follows  that  the 
spheres,  whether  they  are  of  uniform  density,  or 
consist  of  concentric  layers,  with  densities  varying 
according  to  any  law  whatever,  will  act  upon  each 
other  in  the  same  manner  as  if  their  force  resided 
in  their  centres  alone.  But  as  the  bodies  of  the 
solar  system  are  very  nearly  spherical,  they  will  all 
act  upon  one  another,  and  upon  bodies  placed  oa 


152  SIR   ISAAC   NEWTON. 

their  surface,  as  if  they  were  so  many  centres  of 
attraction ;  and  therefore  we  obtain  the  law  of  gravity 
which  subsists  between  spherical  bodies,  namely, 
that  one  sphere  will  act  upon  another  with  a  force 
directly  proportional  to  the  quantity  of  matter,  and 
inversely  as  the  square  of  the  distance  between  the 
centres  of  the  spheres.  From  the  equality  of  action 
and  reaction,  to  which  no  exception  can  be  found, 
Newton  concluded  that  the  sun  gravitated  to  the 
planets,  and  the  planets  to  their  satellites ;  and  the 
earth  itself  to  the  stone  which  falls  upon  its  surface; 
and,  consequently,  that  the  two  mutually  gravitating 
bodies  approached  to  one  another  with  velocities 
inversely  proportional  to  their  quantities  of  matter. 

Having  established  this  universal  law,  Newton 
was  enabled,  not  only  to  determine  the  weight  which 
the  same  body  would  have  at  the  surface  of  the  sun 
and  the  planets,  but  even  to  calculate  the  quantity 
of  matter  in  the  sun,  and  in  all  the  planets  that  had 
satellites,  and  even  to  determine  the  density  or 
specific  gravity  of  the  matter  of  which  they  were 
composed.  In  this  way  he  found  that  the  weight  of 
the  same  body  would  be  twenty-three  times  greater 
at  the  surface  of  the  sun  than  at  the  aurface  of  the 
earth,  and  that  the  density  of  the  earth  was  four  times 
greater  than  that  of  the  sun,  the  planets  increasing 
in  density  as  they  receded  from  the  centre  of  the 
system. 

If  the  peculiar  genius  of  Newton  has  been  dis- 
played in  his  investigation  of  the  law  of  universal 
gravitation,  it  shines  with  no  less  lustre  in  the  pa- 
tience and  sagacity  with  which  he  traced  the  conse- 
quences of  this  fertile  principle. 

The  discovery  of  the  spheroidal  form  of  Jupiter 
by  Cassini  had  probably  directed  the  attention  of 
Newton  to  the  determination  of  its  cause,  and  con 
sequently  to  the  investigation  of  the  true  figure  of 
the  earth.  The  spherical  form  of  the  planets  have 
been  ascribed  by  Copernicus  to  the  gravity  or  natural 


FIGURE    OF    THE    EARTH.  153 

itency  of  their  parts;  but  upon  considering  the 
;h  as  a  body  revolving  upon  its  axis,  Newton 
quickly  saw  that  the  figure  arising  from  the  mutual 
attraction  of  its  parts  must  be  modified  by  another 
force  arising  from  its  rotation.  When  a  body  re- 
volves upon  an  axis,  the  velocity  of  rotation  in- 
creases from  the  poles,  where  it  is  nothing,  to  the 
equator,  where  it  is  a  maximum.  In  consequence 
of  this  velocity  the  bodies  on  the  earth's  surface 
[lave  a  tendency  to  fly  off  from  it,  and  this  tendency 
increases  with  the  velocity.  Hence  arises  a  centrifu- 
gal force  which  acts  in  combination  with  a  force 
of  gravity,  and  which  Newton  found  to  be  the  289th 
part  of  the  force  of  gravity  at  the  equator,  and  de- 
creasing, as  the  cosine  of  the  latitude,  from  the 
equator  to  the  poles.  The  great  predominance  of 
gravity  over  the  centrifugal  force  prevents  the  latter 
irom  carrying  off  any  bodies  from  the  earth's  sur- 
face, but  the  weight  of  all  bodies  is  diminished  by 
;he  centrifugal  force,  so  that  the  weight  of  any  body 
is  greater  at  the  poles  than  it  is  at  the  equator.  If 
we  now  suppose  the  waters  at  the  pole  to  commu- 
nicate with  those  at  the  equator  by  means  of  a  ca- 
nal, one  branch  of  which  goes  from  the  pole  to  the 
centre  of  the  earth,  and  the  other  from  the  centre 
of  the  earth  to  the  equator,  then  the  polar  branch 
of  the  canal  will  be  heavier  than  the  equatorial 
branch,  in  consequence  of  its  weight  not  being  di- 
minished by  the  centrifugal  force,  and,  therefore,  in 
order  that  the  two  columns  maybe  in  equilibrio,  the 
equatorial  one  must  be  lengthened.  Newton  found 
that  the  length  of  the  polar  must  be  to  that  of  the 
equatorial  canal  as  229  to  230,  or  that  the  earth's  polar 
radius  must  be  seventeen  miles  less  than  its  equa- 
jtorial  radius ;  that  is,  that  the  figure  of  the  earth  is 
an  oblate  spheroid,  formed  by  the  revolution  of  an 
ellipse  round  its  lesser  axis.  Hence  it  follows,  that 
the  intensity  of  gravity  at  any  point  of  the  earth's 
surface  is  in  the  inverse  ratio  of  the  distance  of  that , 


154  SIR  ISAAC   NEWTON. 

point  from  the  centre,  and,  consequently,  that  it  di- 
minishes from  the  equator  to  the  poles, — a  result 
which  he  confirmed  by  the  fact,  that  clocks  required 
to  have  their  pendulums  shortened  in  order  to  beat 
true  time  when  carried  from  Europe  towards  the 
equator. 

The  next  subject  to  which  Newton  applied  the 
principle  of  gravity  was  the  tides  of  the  ocean. 
The  philosophers  of  all  ages  have  recognised  the 
connexion  between  the  phenomena  of  the  tides  and 
the  position  of  the  moon.  The  College  of  Jesuits 
at  Coimbra,  and  subsequently  Antonio  de  Dominis 
and  Kepler,  distinctly  referred  the  tides  to  the  attrac- 
tion of  the  waters  of  the  earth  by  the  moon,  but  so 
imperfect  was  the  explanation  which  was  thus  given 
of  the  phenomena,  that  Galileo  ridiculed  the  idea  of 
lunar  attraction,  and  substituted  for  it  a  fallacious 
explanation  of  his  own.  That  the  moon  is  the 
principal  cause  of  the  tides  is  obvious  from  the  well- 
known  fact,  that  it  is  high  water  at  any  given  place 
about  the  time  when  she  is  in  the  meridian  of  that 
place ;  and  that  the  sun  performs  a  secondary  part 
in  their  production  may  be  proved  from  the  circum- 
stance, that  the  highest  tides  take  place  when  the 
sun,  the  moon,  and  the  earth  are  in  the  same  straight 
line,  that  is,  when  the  force  of  the  sun  conspires 
with  that  of  the  moon,  and  that  the  lowest  tides 
take  place  when  the  lines  drawn  from  the  sun  and 
moon  to  the  earth  are  at  right  angles  to  each  other, 
that  is,  when  the  force  of  the  sun  acts  in  opposition 
to  that  of  the  moon.  The  most  perplexing  phe- 
nomenon in  the  tides  of  the  ocean,  and  one  which  is 
still  a  stumbling-block  to  persons  slightly  acquainted 
with  the  theory  of  attraction,  is  the  existence  of 
high  water  on  the  side  of  the  earth  opposite  to  the 
moon,  as  well  as  on  the  side  next  the  moon.  To 
maintain  that  the  attraction  of  the  moon  at  the  same 
instant  draws  the  waters  of  the  ocean  towards  her- 
self, and  also  draws  them  from  the  earth  in  an  oppo- 


TIDES.  155 

•ite  direction,  seems  at  first  sight  paradoxical ;  but 
he  difficulty  vanishes  when  we  consider  the  earth, 
r  rather  the  centre  of  the  earth,  and  the  water  on 
ach  side  of  it  as  three  distinct  bodies  placed  at  dif- 
erent  distances  from  the  moon,  and  consequently 
ttr acted  with  forces  inversely  proportional  to  the 
quaies  of  their  distances.  The  water  nearest  the 
noon  will  be  much  more  powerfully  attracted  than 
he  centre  of  the  earth,  and  the  centre  of  the  earth 
nore  powerfully  than  the  water  farthest  from  the 
noon.  The  consequence  of  this  must  be,  that  the 
raters  nearest  the  moon  will  be  drawn  away  from 
he  centre  of  the  earth,  and  will  consequently  rise 
•om  their  level,  while  the  centre  of  the  earth  will 
e  drawn  away  from  the  waters  opposite  the  moon, 
vhich  will,  as  it  were,  be  left  behind,  and  conse- 
uently  be  in  the  same  situation  as  if  they  were 
aised  from  the  earth  in  a  direction  opposite  to 
lat  in  which  they  are  attracted  by  the  moon, 
"ence  the  effect  of  the  moon's  action  upon  the 
arth  is  to  draw  its  fluid  parts  into  the  form  of  an 
)long  spheroid,  the  axis  of  which  passes  through 
le  moon.  As  the  action  of  the  sun  will  produce 
le  very  same  effect,  though  in  a  smaller  degree, 
le  tide  at  any  place  will  depend  on  the  relative  po- 
tion of  these  two  spheroids,  and  will  be  always 
qual  either  to  the  sum  or  to  the  difference  of  the 
ffects  of  the  two  luminaries.  At  the  time  of  new 
nd  full  moon  the  two  spheroids  will  have  their  axes 
oincident,  and  the  height  of  the  tide,  which  will 
len  be  a  spring  one,  will  be  equal  to  the  sum  of  the 
evations  produced  in  each  spheroid  considered 
Bparately,  while  at  the  first  and  third  quarters  the 
tes  of  the  spheroids  will  be  at  right  angles  to  each 
;her,  and  the  height  of  the  tide,  which  will  tlien  be 
ja  neap  one,  will  be  equal  to  the  difference  of  the 
elevations  produced  in  each  separate  spheroid.  By 
comparing  the  spring  and  neap  tides,  Newton  found 
that  the  force  with  which  the  sun  acted  upon  the 


156  SIR  ISAAC   NEWTON. 

waters  of  the  earth  was  to  that  with  which  the  sun ; 
acted  upon  them  as  4.48  to  1 ; — that  the  force  of  the  | 
moon  produced  a  tide  of  8.63  feet ; — that  of  the  suni 
one  of  1.93  feet; — and  both  of  them  combined,  one 
of  1(H  French  feet, — a  result  which  in  the  open  sea 
does  not  deviate  much  from  observation.  Having 
thus  ascertained  the  force  of  the  moon  on  the  waters 
of  our  globe,  he  found  that  the  quantity  of  mattei 
in  the  moon  was  to  that  in  the  earth  as  1  to  40,  and 
the  density  of  the  moon  to  that  of  the  earth  as  11 
to  9. 

The  motions  of  the  moon,  so  much  within  the 
reach  of  our  own  observation,  presented  a  fine  field 
for  the  application  of  the  theory  of  universal  gravi- 
tation. The  irregularities  exhibited  in  the  lunai 
motions  had  been  known  in  the  time  of  Hipparchus 
and  Ptolemy.  Tycho  had  discovered  the  great  in- 
equality  called  the  variation,  amounting  to  37',  and 
depending  on  the  alternate  acceleration  and  retard- 
ation of  the  moon  in  every  quarter  of  a  revolution, 
and  he  had  also  ascertained  the  existence  of  the 
annual  equation.  Of  these  two  inequalities  Newton 
gave  a  most  satisfactory  explanation.  The  action 
of  the  sun  upon  the  moon  may  be  always  resolved 
into  two,  one  acting  in  the  direction  of  the  line  join- 
ing the  moon  and  earth,  and  consequently  tending 
to  increase  or  diminish  the  moon's  gravity  to  the 
earth,  and  the  other  in  a  direction  at  right  angles  to 
this,  and  consequently  tending  to  accelerate  or  re- 
tard the  motion  in  her  orbit.  Now,  it  was  found  by 
Newton  that  this  last  force  was  reduced  to  nothing, 
or  vanished  at  the  syzigies  or  quadratures,  so  that 
at  these  four  points  the  moon  described  areas  pro- 
portional to  the  times.  The  instant,  however,  that 
the  moon  quits  these  positions,  the  force  under  con* 
sideration,  which  we  may  call  the  tangential  force, 
begins,  and  it  reaches  its  maximum  in  the  four  oc- 
tants. The  force,  therefore,  compounded  of  these 
two  elements  of  the  solar  force,  or  the  diagonal  of 


LUNAR  THEORY.  157 

i the  parallelogram  which  they  form,  is  no  longer 
directed  to  the  earth's  centre,  but  deviates  from  it  at 
a  maximum  about  30  minutes,  and  therefore  affects 
the  angular  motion  of  the  moon,  the  motion  being 
accelerated  in  passing  from  the  quadratures  to  the 
syzigies,  and  retarded  in  passing  from  the  syzigies 
to  the  quadratures.  Hence  the  velocity  is  in  its 
mean  state  in  the  cctanls,  a  maximum  in  the  syzi- 
gies, and  a  minimum  in  the  quadratures. 

Upon  considering  the  influence  of  the  solar  force 
in  diminishing  or  increasing  the  moon's  gravity  to 
the  earth,  Newton  saw  that  her  distance  and  her 
periodic  time  must  from  this  cause  be  subject  to 
change,  and  in  this  way  he  accounted  for  the  annual 
equation  observed  by  Tycho.  By  the  application 
of  similar  principles,  he  explained  the  cause  of  the 
motion  of  the  apsides,  or  of  the  greater  axis  of  the 
moon's  orbit,  which  has  an  angular  progressive  mo- 
tion of  3°  4'  nearly  in  the  course  of  one  lunation ; 
and  he  showed  that  the  retrogradation  of  the  nodes, 
amounting  to  3'  10"  daily,  arose  from  one  of  the  ele- 
ments of  the  solar  force  being  exerted  in  the  plane 
of  the  ecliptic,  and  not  in  the  plane  of  the  moon's 
orbit,  the  effect  of  which  was  to  draw  the  moon 
down  to  the  plane  of  the  ecliptic,  and  thus  cause  the 
[me  of  the  nodes,  or  the  intersection  of  these  two 
planes,  to  move  in  a  direction  opposite  to  that  of  the 
moon.  The  lunar  theory  thus  blocked  out  by  New- 
ton, required  for  its  completion  the  labours  of  another 
century.  The  imperfections  of  the  fluxionary  cal- 
culus prevented  him  from  explaining  the  other  ine- 
qualities of  the  moon's  motions,  and  it  was  reserved 
to  Euler,  D'Alembert,  Clairaut,  Mayer,  and  Laplace 
to  bring  the  lunar  tables  to  a  high  degree  of  perfec- 
tion, and  to  enable  the  navigator  to  determine  his 
longitude  at  sea  with  a  degree  of  precision  which 
the  most  sanguine  astronomer  could  scarcely  have 
anticipated. 

By  the  consideration  of  the  retrograde  motion  of 
O 


158  SIR   ISAAC   NEWTOff. 

the  moon's  nodes,  Newton  was  led  to  discover  the 
cause  of  the  remarkable  phenomenon  of  the  preces- 
sion of  the  equinoctial  points,  which  moved  50"  an- 
nually, and  completed  the  circuit  of  the  heavens  in 
25,920  years.  Kepler  had  declared  himself  incapa- 
ble of  assigning-  any  cause  for  this  motion,  and  we 
do  not  believe  that  any  other  astronomer  ever  made 
the  attempt.  From  the  spheroidal  form  of  the  earth, 
it  may  be  regarded  as  a  sphere  with  a  spheroidal 
ring  surrounding  its  equator,  one-half  of  the  ring 
beii^  "ibove  the  plane  of  the  ecliptic  and  the  other 
half  below  it.  Considering  this  excess  of  matter 
as  a  system  of  satellites  adhering  to  the  earth's  sur- 
face,  Newton  saw  that  the  combined  actions  of  the 
sun  and  moon  upon  these  satellites  tended  to  pro- 
duce a  retrogradation  in  the  nodes  of  the  circles 
which  they  described  in  their  diurnal  rotation,  and 
that  the  sum  of  all  the  tendencies  being  communi- 
cated to  the  whole  mass  of  the  planet,  ought  to  pro- 
duce a  slow  retrogradation  of  the  equinoctial  points. 
The  effect  produced  by  the  motion  of  the  sun  he 
found  to  be  40",  and  that  produced  by  the  action  of , 
the  moon  10". 

Although  there  could  be  little  doubt  that   the 
comets  were  retained  in  their  orbits  by  the  same 
laws  which  regulated  the  motions  of  the  planets, 
yet  it  was  difficult  to  put  this  opinion  to  the  test  of 
observation.     The  visibility  of  comets  only  in  a 
small  part  of  their  orbits  rendered  it  difficult  to  as- , 
certain  their  distance  and  periodic  times,  and  as  theii  •• 
periods  were  probably  of  great  length,  it  was  impos-  \ 
sible  to  correct  approximate  results  by  repeated  ob- 
servation.    Newton,  however,  removed  this  diffi-  j 
culty,  by  showing  how  to  determine  the  orbit  of  2  i 
comet,  namely,  the  form  and  position  of  the  orbil  i 
and  the  periodic  time,  by  three  observations.    By  [ 
applying  this  method  to  the  comet  of  1680,  he  cal- 
culated the  elements  of  its  orbit,  and  from  the  agree- 
ment of  the  comouted  places  with  those  which 


COMETS.  159 

vere  observed,  he  justly  inferred  that  the  motions 
)f  comets  were  regulated  by  the  same  laws  as  those 
>f  the  planetary  bodies.     This  result  was  one  of 
preat  importance ;  for  as  the  comets  enter  our  sys- 
em  in  every  possible  direction,  and  at  all  angles 
vith  the  ecliptic,  and  as  a  great  part  of  their  orbits 
xtend  far  beyond  the  limits  of  the  solar  system,  it 
emonstrated  the  existence  of  gravity  in  spaces  far 
removed  beyond  the  planet,  and  proved  that  the  law 
)f  the  inverse  ratio  of  the  squares  of  the  distance 
Fas  true  in  every  possible  direction,  and  at  very  re- 
note  distances  from  the  centre  of  our  system.* 
Such  is  a  brief  view  of  the  leading  discoveries 
rhich  the  Principia  first  announced  to  the  world. 
The  grandeur  of  the  subjects  of  which  it  treats,  the 
eautiful  simplicity  of  the  system  which  it  unfolds, 
he  clear  and  concise  reasoning  by  which  that  sys- 
,em  is  explained,  and  the  irresistible  evidence  by 
ivhich   it  is  supported  might  have  ensured  it  the 
warmest  admiration  of  contemporary  mathemati- 
ians,  and  the  most  welcome  reception  in  all  the 
chools  of  philosophy  throughout   Europe.     This, 
lowever,  is  not  the  way  in  which  great  truths  are 
generally  received.     Though  the  astronomical  dis- 
overies  of  Newton  were  not  assailed  by  the  class 
>f  ignorant  pretenders  who   attacked  his    optical 
writings,  yet  they  were  every  where  resisted  by  the 
rrors  and  prejudices  which  had  taken  a  deep  hold 
ven  of  the  strongest  minds.     The  philosophy  of 
Descartes   was    predominant   throughout   Europe. 
Appealing  to  the  imagination,  and  not  to  the  reason 
f  mankind,  it  was  quickly  received  into  popular 
avour,  and  the  same  causes  which  facilitated  its  in- 
roduction  extended  its  influence,  and  completed  its 
ominion  over  the  human  mind.     In  explaining  all 
the  movements  of  the  heavenly  bodies  by  a  system 

*  In  writing  to  Flamstead,  Newton  requests  from  him  the  long  diame- 
ters of  the  orbits  cf  Jupiter  and  Saturn,  that  he  "  may  see  how  the  ses* 
guialt&raJ  proportion  Jills  the  heavens.'' 


160  SIR   ISAAC   NEWTON. 

of  vortices  in  a  fluid  medium  diffused  through  the 
universe,  Descartes  had  seized  upon  an  analogy  of 
the  most  alluring  and  deceitful  kind.  Those  who 
had  seen  heavy  bodies  revolving  in  the  eddies  of  a 
whirlpool,  or  in  the  gyrations  of  a  vessel  of  water 
thrown  into  a  circular  motion,  had  no  difficulty  in 
conceiving  how  the  planets  might  revolve  round  the 
sun  by  analogous  movements.  The  mind  instantly 
grasped  at  an  explanation  of  so  palpable  a  character, 
and  which  required  for  its  development  neither  the 
exercise  of  patient  thought  nor  the  aid  of  mathe- 
matical skill.  The  talent  and  perspicuity  with  which 
the  Cartesian  system  was  expounded,  and  the  show 
of  experiments  with  which  it  was  sustained,  con- 
tributed powerfully  to  its  adoption,  while  it  derived  a 
still  higher  sanction  from  the  excellent  character 
and  the  unaffected  piety  of  its  author. 

Thus  intrenched,  as  the  Cartesian  system  was,  in 
the  strongholds  of  the  human  mind,  and  fortified  by 
its  most  obstinate  prejudices,  it  was  not  to  be  won- 
dered at  that  the  pure  and  sublime  doctrines  of  the 
Principia  were  distrustfully  received  and  persever- 
ingly  resisted.  The  uninstructed  mind  could  not 
readily  admit  the  idea,  that  the  great  masses  of  the 
planets  were  suspended  in  empty  space,  and  retained 
in  then  orbits  by  an  invisible  influence  residing  in 
the  sun ;  and  even  those  philosophers  who  had  been 
accustomed  to  the  rigour  of  true  scientific  research, 
and  who  possessed  sufficient  mathematical  skill  for 
the  examination  of  the  Newtonian  doctrines,  viewed 
them  at  first  as  reviving  the  occult  qualities  of  the 
ancient  physics,  and  resisted  their  introduction  with 
a  pertinacity  which  it  is  not  easy  to  explain.  Preju- 
diced, no  doubt,  in  favour  of  his  own  metaphysical 
views,  Leibnitz  himself  misapprehended  the  princi- 
ples of  the  Newtonian  philosophy,  and  endeavoured 
to  demonstrate  the  truths  in  the  Principia  by  the  appli- 
cation of  different  principles.  Huygens,  who  above  all 
other  men  was  qualified  to  appreciate  the  new  philo* 


NEWTONIAN  PHILOSOPHY.  161 

sophy,  rejected  the  doctrine  of  gravitation  as  existing 
?  between  the  individual  particles  of  matter,  and  re- 
;  ceived  it  only  as  an  attribute  of  the  planetary  masses, 
f  John  Bernouilli,  one  of  the  first  mathematicians  of 
j  his  age,  opposed  the  philosophy  of  Newton.  Mai- 
Iran,  in  the  early  part  of  his  life,  was  a  strenuous  de- 
I  fender  of  the  system  of  vortices.  Cassini  and  Ma- 
Iraldi  were  quite  ignorant  of  the  Principia,  and  occu- 
ipied  themselves  with  the  most  absurd  methods  of 
I  calculating  the  orbits  of  comets  long  after  the  New- 
I  toman  method  had  been  established  on  the  most 
I  impregnable  foundation ;  and  even  Fontenelle,  a  man 
I  of  liberal  views  and  extensive  information,  continued, 
I  throughout  the  whole  of  his  life,  to  maintain  the 
I  doctrines  of  Descartes. 

The  Chevalier  Louville  of  Paris  had  adopted  the 
I  Newtonian  philosophy  before  1720.  S'Gravesande 
I  had  introduced  it  into  the  Dutch  universities  at  a 
somewhat  earlier  period,  and  Maupertuis,  in  conse- 
quence of  a  visit  which  he  paid  to  England  in  1728, 
became  a  zealous  defender  of  it;  but  notwithstand- 
ing these  and  some  other  examples  that  might  be 
quoted,  we  must  admit  the  truth  of  the  remark  of 
Voltaire,  that  though  Newton  survived  the  publica- 
tion of  the  Principia  more  than  forty  years,  yet  at 
the  time  of  his  death  he  had  not  above  twenty  fol- 
lowers out  of  England. 

With  regard  to  the  progress  of  the  Newtonian 
philosophy  in  England,  some  difference  of  opinion 
has  been  entertained.  Professor  Playfair  gives  the 
following  account  of  it.  i;  In  the  universities  of 
England,  though  the  Aristotelian  physics  had  made 
an  obstinate  resistance,  they  had  been  supplanted 
by  the  Cartesian,  which  became  firmly  established 
about  the  time  when  their  foundation  began  to  be? 
sapped  by  the  general  progress  of  science,  and  par- 
ticularly by  the  discoveries  of  Newton.  For  more 
than  thirty  years  after  the  publication  of  these  dis- 
coveries, the  system  of  vortices  kept  its  ground;  and 
02 


162  SIR   ISAAC  NEWTON. 

ia  translation  from  the  French  into  Latin  of  the 
sics  of  feohault,  a  work  entirely  Cartesian,  con- 
tinued at  Cambridge  to  be  the  text^-for  philosophical 
instruction."  About  the  year  1718,^  new  and  more 
elegant  translation  of  the  same  book  was  published 
by  Dr.  Samuel  Clarke,  with  the  addition  of  notes,  in 
which  that  profound  and  ingenious  writer  explained 
the  views  of  Newton  on  the  principal  objects  of 
discussion,  so  that  the  notes  contained  virtually  a 
refutation  of  the  text;  they  did  so,  however,  only 
virtually,  all  appearance  of  argument  and  contro- 
versy being  carefully  avoided.  Whether  this  escaped 
the  notice  of  the  learned  doctor  or  not  is  uncertain, 
but  the  new  translation,  from  its  better  Latinity,  and 
the  name  of  the  editor,  was  readily  admitted  to  all 
the  academical  honours  which  the  old  one  had  en- 
joyed. Thus  the  stratagem  of  Dr.  Clarke  com- 
pletely succeeded  ;  the  tutor  might  prelect  from  the 
text,  but  the  pupil  would  sometimes  look  into  the 
notes ;  and  error  is  never  so  sure  of  being  exposed 
as  when  the  truth  is  placed  close  to  it,  side  by  side, 
without  any  thing  to  alarm  prejudice,  or  awaken  - 
from  its  lethargy  the  dread  of  innovation.  Thus, 
therefore,  the  Newtonian  philosophy  first  entered 
the  university  of  Cambridge  under  the  protection  of 
the  Cartesian."  To  this  passage  Professor  Playfair 
adds  the  following  as  a  note  : — 

"  The  universities  of  St.  Andrew's  and  Edinburgh 
were,  I  believe,  the  first  in  Britain  where  the  New- 
sman philosophy  was  made  the  subject  of  the  aca- 
demical prelections.  For  this  distinction  they  are 
Indebted  to  James  and  David  Gregory,  the  first  in 
$ome  respects  the  rival,  but  both  the  friends  of 
Newton.  Whiston  bewails,  in  the  anguish  of  his 
heart,  the  difference,  in  this  respect,  between  those 
universities  and  his  own.  David  Gregory  taught  in 
Edinburgh  for  several  years  prior  to  1690,  when  he 
removed  to  Oxford ;  and  Whiston  says,  '  He  had 
already  caused  several  of  his  scholars  to  keep  acts,; 


NEWTONIAN   PHILOSOPHY.  163 

as  we  call  them,  upon  several  branches  of  the  New- 
Ionian  philosophy,  while  we  at  Cambridge,  poor 
I  wretches,  were  ignominiously  studying  the  fictitious 
|  hypotheses  of  the  Cartesians.'*    I  do  not,  however, 
i  mean  to  say,  that  from  this  date  the  Cartesian  phi- 
i losophy  was  expelled  from  those  universities;  the 
|  Physics  of  Rohault  were  still  in  use  as  a  text-book, — 
I  at  least  occasionally,  to  a  much  later  period  than  this, 
L  and  a  great  deal,  no  vx^^bt,  depended  on  the  character 
I  of  the  individual.     Professor  Keill  introduced  the 
\  Newtonian  philosophy  in  his  lectures  at  Oxford  in 
;  1697 ;  but  the  instructions  of  the  tutors,  which  con- 
E  stitute  the  real  and  efficient  system  of  the  univer- 
|  sity,  were  not  cast  in  that  mould  till  long  afterward." 
Adopting  the  same  view  of  the  subject,  Mr.  Dugald 
Stewart  has  stated,  "  that  the  philosophy  of  Newton 
was  publicly  taught  by  David  Gregory  at  Edinburgh, 
and  by  his  brother,  James  Gregory,  at  St.  Andrew's,! 
before  it  was  able  to  supplant  the  vortices  of  Des- 
cartes in  that  very  university  of  which  Newton 
was  a  member.     It  was  in  the  Scottish  universities 
that  the  philosophy  of  Locke,  as  well  as  that  of 
Newton,  was  first  adopted  as  a  branch  of  academi- 
cal education." 

Anxious  as  we  should  have  been  to  have  awarded 
to  Scotland  the  honour  of  having  first  adopted  the 
Newtonian  philosophy,  yet  a  regard  for  historical 
truth  compels  us  to  take  a  different  view  of  the  sub- 
ject. It  is  well  known  that  Sir  Isaac  Newton  de- 
livered lectures  on  his  own  philosophy  from  the 
Lucasian  chair  before  the  publication  of  the  Prin- 
cipia;  and  in  the  very  page  of  Whiston's  life  quoted 
by  Professor  Playfair,  he  informs  us  that  he  had 
heard  him  read  such  lectures  in  the  public  schools, 


*  Whiston's  Memoirs  of  his  own  Life. 

f  "  Dr.  Reid  states,  that  James  Gregory,  Professor  of  Philosophy  at 
St.  Andrew's,  printed  a  thesis  at  Edinburgh  in  1690,  containing  twenty- 

ftvo  nr»sifinn<5    nf  which  t\*r»3ntv_twA  w*ir*>  n  /»mnn*>fiH  r»f  N>.wtnn's   Prin« 


cipia." 


164  SIR   ISAAC  NEWTON. 

though  at  that  time  he  did  not  at  all  understand 
them.  Newton  continued  to  lecture  till  1699,  and 
occasionally,  we  presume,  till  1703,  when  Whiston 
became  his  successor,  having  been  appointed  his 
deputy  in  1699.  In  both  of  these  capacities  Wins- 
ton delivered  in  the  public  schools  a  course  of  lec- 
tures on  astronomy,  and  a  course  of  physico-mathe- 
matical  lectures,  in  which  the  mathematical  philoso- 
phy of  Newton  was  explained  and  demonstrated, 
and  both  these  courses  were  published,  the  one  in 
1707,  and  the  other  in  1710,  "  for  the  use  of  the 
young  men  in  the  university."  In  1707,  the  cele- 
brated blind  mathematician  Nicholas  Saunderson 
took  up  his  residence  in  Christ's  College  without 
being  admitted  a  member  of  that  body.  The  society 
not  only  allotted  to  him  apartments,  but  gave  him 
the  free  use  of  their  library.  With  the  concurrence 
of  Whiston  he  delivered  a  course  of  lectures  "  on 
the  Principia,  Optics,  and  Universal  Arithmetic  of 
Newton,"  and  the  popularity  of  these  lectures  was 
so  great,  that  Sir  Isaac  corresponded  on  the  subject 
of •  -them  with  their  author ;  and  on  the  ejection  of 
Whiston  from  the  Lucasian  chair  in  1711,  Saunderson 
was  appointed  his  successor.  In  this  important  office 
he  continued  to  teach  the  Newtonian  philosophy  till 
the  time  of  his  death,  which  took  place  in  1739. 

But  while  the  Newtonian  philosophy  was  thus 
regularly  taught  in  Cambridge,  after  the  publication 
of  the  Principia,  there  were  not  wanting  other  exer- 
tions for  accelerating  its  progress.  About  1694,  the 
celebrated  Dr.  Samuel  Clarke,  while  an  under-grad- 
uate,  defended,  in  the  public  schools,  a  question  taken 
from  the  Newtonian  philosophy;  and  his  translation 
of  Rohault's  Physics,  which  contains  'references  in 
the  notes  to  the  Principia,  and  which  was  published 
in  1697  (and  not  in  1718,  as  stated  by  Professor 
Playfair),  shows  how  early  the  Cartesian  system 
was  attacked  by  the  disciples  of  Newton.  The 
author  of  the  Life  of  Saunderson  informs  us,  that 


PROGRESS  IN  ENGLAND.         165 

>lic  exercises  or  acts  founded  on  every  part  of  the 
fewtonian  system  were  veiy  common  about  1707, 
and  so  general  \vere  such  studies  in  the  university, 
!  that  the  Principia  rose  to  four  times  its  original 
•  price.*  One  of  the  most  ardent  votaries  of  the 
f-  Newtonian  philosophy  was  Dr.  Laughton,  who  had 
t  been  tutor  in  Glare  Hall  from  1694,  and  it  is  probable 
Ithat  during  the  whole,  or  at  least  a  greater  part,  of 
[his  tutorship  he  had  inculcated  the  same  doctrines. 
lln  1709-10,  when  he  was  proctor  of  that  college,  in- 
^  stead  of  appointing  a  moderator,  he  discharged  the 
\  office  himself,  and  devoted  his  most  active  exertions 
|  to  the  promotion  of  mathematical  knowledge.  Pre- 
(vious  to  this,  he  had  even  published  a  paper  of  ques- 
tions on  the  Newtonian  philosophy,  which  appear  to 
have  been  used  as  theses  for  disputations ;  and  such 
was  his  ardour  and  learning  that  they  powerfully 
contributed  to  the  popularity  of  his  college.  Be- 
tween 1706  and  1716,  the  year  of  his  death,  the  cele- 
brated Roger  Cotes,  the  friend  and  disciple  of  New- 
ton, filled  the  Plumian  chair  of  astronomy  and  ex- 
perimental philosophy  at  Cambridge.  During  this 
period  he  edited  the  second  edition  of  the  Principia, 
which  he  enriched  with  an  admirable  preface,  and 
thus  contributed,  by  his  writings  as  well  as  by  his 
lectures,  to  advance  the  philosophy  of  his  master. 
About  the  same  time,  the  learned  Dr.  Bentley,  who 
first  made  known  the  philosophy  of  his  friend  to  the 
readers  of  general  literature,  filled  the  high  office  of 
master  of  Trinity  College,  and  could  not  fail  to  have 
exerted  his  utmost  influence  in  propagating  doctrines 
which  he  so  greatly  admired.  Had  any  opposition 
been  offered  to  the  introduction  of  the  true  system 
of  the  universe,  the  talents  and  influence  of  these 
individuals  would  have  immediately  suppressed  it; 
but  no  such  opposition  seems  to  have  been  made ; 

*  Nichols's  Literary  Anecdotes>  vol.  iii.  p.  322.  Cotes  states  in  hi« 
preface  to  the  second  edition  of  the  Principia,  that  copies  of  the  first 
edition  could  only  be  obtained  at  an  immense  price. 


166  SIR   ISAAC   NEWTON. 

and  though  there  may  have  been  individuals  at  Cam- 
bridge ignorant  of  mathematical  science,  who  ad- 
hered to  the  system  of  Descartes,  and  patronised 
the  study  of  the  Physics  of  Rohault,  yet  it  is  pro- 
bable that  similar  persons  existed  in  the  universities 
of  Edinburgh  and  St.  Andrew's ;  and  we  cannot  re- 
gard their  adherence  to  error  as  disproving  the  gen- 
eral fact,  that  the  philosophy  of  Newton  was  quickly 
introduced  into  all  the  universities  of  Great  Britain. 
But  while  the  mathematical  principles  of  the  New- 
tonian system  were  ably  expounded  in  our  seats  of 
learning,  its  physical  truths  were  generally  studied, 
and  were  explained  and  communicated  to  the  public 
by  various  lecturers  on  experimental  philosophy. 
The  celebrated  Locke,  who  was  incapable  of  under- 
standing the  Prlncipia  from  his  want  of  mathemati- 
cal knowledge,  inquired  ofjHuygens  if  all  the  mathe- 
matical propositions  in  that  work  were  true.  When 
he  was  assured  that  he  might  depend  upon  their  cer- 
tainty, he  took  them  for  granted,  and  carefully  ex- 
amined the  reasonings  and  corollaries  deduced  from 
them.  In  this  manner  he  acquired  a  knowledge  of 
the  physical  truths  in  the  Principia,  and  became  a 
firm  believer  in  the  discoveries  which  it  contained. 
In  the  same  manner  he  studied  the  treatise  on  Op- 
tics, and  made  himself  master  of  every  part  of  it 
which  was  not  mathematical.*  From  a  manuscript 
of  Sir  Isaac  Newton's,  entitled  "  A  demonstration 
that  the  planets,  by  their  gravity  towards  the  sun, 
may  move  in  ellipses,!  found  among  the  papers  of 
Mr.  Locke,  and  published  by  Lord  King,"  it  would 
appear  that  he  himself  had  been  at  considerable 
trouble  in  explaining  to  his  friend  that  interesting 
;  doctrine.  Thissmanuscript  is  endorsed,  "  Mr.  New- 
ton, March,  1689."  It  begins  with  three  hypotheses 

*  Preface  to  Desaguliers's  Experimental  Philosophy.  Dr.  Desaguliera 
states  that  he  was  told  this  anecdote  several  times  by  Sii  Isaac  Newtou 
himself. 

t  The  Life  of  John  Locke,  p.  209-215,  Lond.  1829. 


PROGRESS   IN   ENGLAND. 


(the  first  two  being  the  two  laws  of  motion,  and  the 
third  the  parallelogram  of  motion),  which  introduce 
the  proposition  of  the  proportionality  of  the  areas 
to  the  times  in  motions  round  an  immoveable  centre 
of  attraction.*  Three  lemmas,  containing  properties 
of  the  ellipse,  then  prepare  the  reader  for  the  cele- 
brated proposition,  that  when  a  body  moves  in  an 
ellipse,!  the  attraction  is  reciprocally  as  the  square 
of  the  distance  of  the  body  from  the  focus  to  which 
it  is  attracted.  These  propositions  are  demonstrated 
in  a  more  popular  manner  than  in  the  Principia,  but 
there  can  be  no  doubt  that,  even  in  their  present 
modified  form,  they  were  beyond  the  capacity  of 
Mr.  Locke. 

Dr.  John  Keill  was  the  first  person  who  publicly 
taught  natural  philosophy  by  experiments.  Desa- 
guliers  informs  us  that  this  author  "  laid  down  very 
simple  propositions,which  he  proved  by  experiments, 
and  from  these  he  deduced  others  more  compound, 
which  he  still  confirmed  by  experiments,  till  he  had 
instructed  his  auditors  in  the  laws  of  motion,  the 
principles  of  hydrostatics  and  optics,  and  some  of 
the  chief  propositions  of  Sir  Isaac  Newton  concern- 
ing light  and  colours.  He  began  these  courses  in 
Oxford  about  the  year  1704  or  1705,  and  in  that  way 
introduced  the  love  of  the  Newtonian  philosophy." 
When  Dr.  Keill  left  the  university,  Desaguliers  be- 
gan to  teach  the  Newtonian  philosophy  by  experi- 
ments. He  commenced  his  lectures  at  Harthall  in 
Oxford,  in  1710,  and  delivered  more  than  a  hundred 
and  twenty  courses ;  and  when  he  went  to  settle  in 
London  in  1713,  he  informs  us  that  he  found  "  the 
Newtonian  philosophy  generally  received  among 
persons  of  all  ranks  and  professions,  and  even 
among  the  ladies  by  the  help  of  experiments." 
Such  were  the  steps  by  which  the  Newtonian  phi- 
losophy was  established  in  Great  Britain.  From 

*  Principia,  lib.  i.  prop.  i. 


168  SIR    ISAAC   NEWTON. 

the  time  of* the  publication  of  the  Principia,  its 
mathematical  doctrines  formed  a  regular  part  of  aca- 
demical education;  and  before  twenty  years  had 
elapsed,  its  physical  truths  were  communicated  to 
the  public  in  popular  lectures  illustrated  by  experi- 
ments, and  accommodated  to  the  capacities  of  those 
who  were  not  versed  in  mathematical  knowledge. 
The  Cartesian  system,  though  it  may  have  lingered 
for  a  while  in  the  recesses  of  our  universities,  was 
soon  overturned ;  and  long  before  his  death,  Newton 
enjoyed  the  high  satisfaction  of  seeing  his  philoso- 
phy triumphant  in  his  native  land. 


CHAPTER  XII. 

Doctrine  cf  Infinite  Quantities — Labours  of  Pappus — Kepler — Cavalert 
— Roberval — Fermat — Wall  is — Newton  discovers  the  Hmomial  Theo- 
rem— and  the  Doctrine  of  Fluxions  in  1666 — His  Manuscript  Work 
containing  this  Doctrine  communicated  to  his  Friends — His  Treatise 
on  Fluxions— His  Mathematical  Tracts — His  Universal  Arithmetic — 
His  Methodus  Differentialis—His  Geometria  Analytica — His  Solu' 
tion  of  the  Problems  proposed  by  Bernouilli  aud  Leibnitz — Account 
of  the  celebrated  Dispute  respecting  the  Invention  of  Ftuxions—Com- 
mercium  Epistolicum — Report  of  the  Royal  Society -^General  View 
of  the  Controversy. 

PREVIOUS  to  the  time  of  Newton,  the  doctrine  of 
infinite  quantities  had  been  the  subject  of  profound 
study.  The  ancients  made  the  first  step  in  this 
curious  inquiry  by  a  rude  though  ingenious  attempt 
to  determine  the  area  of  curves.  The  method  of 
exhaustions  which  was  used  for  this  purpose  con- 
sisted in  finding  a  given  rectilineal  area  to  which  the 
inscribed  and  circumscribed  polygonal  figures  con- 
tinually approached  by  increasing  the  number  of 
their  sides.  This  area  was  obviously  the  area 
of  the  curve,  and  in  the  case  of  the  parabola  it  was 
found  by  Archimedes  to  be  two-thirds  of  the  area 


INFINITE    QUANTITIES.  169 

ied  by  multiplying  the  ordinate  by  the  abscissa, 
ough  the  synthetical  demonstration  of  the  re- 
ts was  perfectly  conclusive,  yet  the  method  itself 
was  limited  and  imperfect. 

The  celebrated  Pappus  of  Alexandria  followed 
Archimedes  in  the  same  inquiries ;  and  in  his  demon- 
stration of  the  property  of  the  centre  of  gravity 
of  a  plane  figure,  by  which  we  may  determine  the 
solid  formed  by  its  revolution,  he  has  shadowed 
forth  the  discoveries  of  later  times. 
In  his  curious  tract  on  Stereometry,  published  in 
615,  Kepler  made  some  advances  in  the  doctrine 
»f  infinitesimals.  Prompted  to  the  task  by  a  dis- 
pute with  the  seller  of  some  casks  of  wine,  he 
studied  the  measurement  of  solids  formed  by  the 
revolution  of  a  curve  round  any  line  whatever. 
In  solving  some  of  the  simplest  of  Jhese  problems, 
he  conceived  a  circle  to  be  formed  of  an  infinite 
number  of  triangles  having  all  their  vertices  in  the 
centre,  and  their  infinitely  small  bases  in  the  circum- 
ference of  the  circle,  and  by  thus  rendering  familiar 
the  idea  of  quantities  infinitely  great  and  infinitely 
small,  he  gave  an  impulse  to  this  branch  of  mathe- 
matics. The  failure  of  Kepler,  too,  in  solving  some 
of  the  more  difficult  of  the  problems  which  he  him- 
self proposed  roused  the  attention  of  geometers, 
and  seems  particularly  to  have  attracted  the  notice 
of  Cavaleri. 

This  ingenious  mathematician  was  born  at  Milan 
in  1598,  and  was  Professor  of  Geometry  at  Bologna. 
In  his  method  of  Indivisibles,  which  was  published 
in  1635,  he  considered  a  line  as  composed  of  an  in- 
finite number  of  points,  a  surface  of  an  infinite 
number  of  lines,  and  a  solid  of  an  infinite  number 
of  surfaces ;  and  he  lays  it  down  as  an  axiom  that 
the  infinite  sums  of  such  lines  and  surfaces  have  the 
same  ratio  when  compared  with  the  linear  or  super- 
ficial unit,  as  the  surfaces  and  solids  which  are  to 
be  determined.  As  it  is  not  true  that  an  infinite 
P 


170  SIR    ISAAC   NEWTON. 

number  of  infinitely  small  points  can  make  a  Jin 
or  an  infinite  number  of  infinitely  small  lines  a  sur- 
face, Pascal  removed  this  verbal  difficulty  by  con- 
sidering a  line  as  composed  of  an  infinite  number 
of  infinilely  short  lines,  a  surface  as  composed  of 
an  infinite  number  of  infinitely  narrow  parallelo- 
grams, and  a  solid  of  an  infinite  number  of  infinitely 
thin  solids.  But,  independent  of  this  correction, 
the  conclusions  deduced  by  Cavaleri  are  rigorously 
true,  and  his  method  of  ascertaining  the  ratios  of 
areas  and  solids  to  one  another,  and  the  theorems « 
which  he  deduced  from  it  may  be  considered  as 
forming  an  era  in  mathematics. 

By  the  application  of  this  method,  Roberval  and 
Toricelli  showed  that  the  area  of  the  cycloid  is  three 
times  that  of  its  generating  circle,  and  the  former 
extended  the  method  of  Cavaleri  to  the  case  where 
the  powers  of  the  terms  of  the  arithmetical  pro- 
gression to  be  summed  were  fractional. 

In  applying  the  doctrine  of  infinitely  small  quanti- 
ties to  determine  the  tangents  of  curves,  and  the 
maxima  and  minima  of  their  ordinates,  both  Ro- 
berval and  Fermat  made  a  near  approach  to  the 
invention  of  fluxions — so  near  indeed  that  both 
Lagrange  and  Laplace*  have  pronounced  the  latter 
to  be  the  true  inventer  of  the  differential  calculus. 
Roberval  supposed  the  poh  t  which  describes  a 
curve  to  be  actuated  by  two  motions,  by  the  compo- 
sition of  which  it  moves  in  the  direction  of  a  tan- 
gent; and  had  he  possessed  the  method  of  fluxions, 
he  could,  in  every  case,  have  determined  the  rela- 
tive velocities  of  these  motions,  which  depend  on 
the  nature  of  the  curve,  and  consequently  the 
direction  of  the  tangent  which  he  assumed  to  be  in 
the  diagonal  of  a  parallelogram  whose  sides  had  the 

*  "  On  pent  regarder  Fermat,"  says  Lagrange,  "  comme  le  premier 
inventeur  des  nouveaux  calculs  ;"  and  Laplace  observes,  "II  paraitque 
Fermat,  le  veritable  inventeur  du  calcnl  diflerentiel,  Pait  envisage  comma 
un  cas  particulier  d*j  celui  des  di^*erences,"  &c. 


INFINITE    QUANTITIES.  171 

same  ratio  as  the  velocities.  But  as  he  was  able 
ito  determine  these  velocities  only  in  the  conic  sec- 
|tions,  &c.  his  ingenious  method  had  but  few  appli- 
cations. 

The  labours  of  Peter  Fermat,  a  counsellor  of  the 
parliament  of  Toulouse,  approached  still  nearer  to 
the  fluxionary  calculus.  In  his  method  of  deter- 
mining the  maxima  and  minima  of  the  ordinates  of 
curves,  he  substitutes  x-\-e  for  the  independent 
variable  x  in  the  function  which  is  to  become  a 
.maximum,  and  as  these  two  expressions  should  be 
equal  when  e  becomes  infinitely  small  or  0,  he  frees 
this  equation  from  surds  and  radicals,  and  after  di- 
viding the  whole  by  e,  e  is  made  =  0,  and  the  equation 
for  the  maximum  is  thus  obtained.  Upon  a  similar 
principle  he  founded  his  method  of  drawing  tangents 
to  curves.  But  though  the  methods  thus  used  by 
Fermat  are  in  principle  the  same  with  those  which 
connect  the  theory  of  tangents  and  of  maxima 
and  minima  with  the  analytical  method  of  exhibit- 
ing the  differential  calculus,  yet  it  is  a  singular  ex- 
ample of  national  partiality  to  consider  the  inventer 
of  these  methods  as  the  inventer  of  the  method  of, 
fluxions. 

"  One  might  be  led,"  says  Mr.  Herschel,  "  to  sup- 
pose by  Laplace's  expression  that  the  calculus  of 
finite  differences  had  then  already  assumed  a  sys- 
tematic form,  and  that  Fermat  had  actually  observed 
the  relation  between  the  two  calculi,  and  derived 
the  one  from  the  other.  The  latter  conclusion 
would  scarcely  be  less  correct  than  the  former.  No 
method  can  justly  be  regarded  as  bearing  any  anal- 
ogy to  the  differential  calculus  which  does  not  lay 
down  a  system  of  rules  (no  matter  on  what  consid- 
erations founded,  by  what  names  called,  or  by  what 
extraneous  matter  enveloped)  by  means  of  which 
the  second  term  of  the  development  of  any  function 
of  x-{-e  in  powers  of  e,  can  be  correctly  calculated, 
•quae  extendet  se,'  to  use  Newton's  expression, 


172  SIR   ISAAC   NEWTON. 

*  citra  ullum  molestum  calculum  in  terminis  surdis 
seque  ac  in  integris  procedens.'    It  would  be  strange 
to  suppose  Fermat  or  any  other  in  possession  of 
such  a  method  before  any  single  surd  quantity  had 
ever  been  developed  in  a  series.     But,  in  point  of 
fact,  his  writings  present  no  trace  of  the  kind ;  and 
this,  though  fatal  to  his  claim,  is  allowed  by  both  the 
geometers  cited.     Hear  Lagrange's  candid  avowal. 

*  II  fait  disparaitre  dans  cette  equation,'  that  of  the 
maximum  between  x  and  e,  '  les  radicaux  et  les  frac- 
tions  s'il  y  en  a.'    Laplace,  too,  declares  that '  il  sa- 
voit  etendre  son  calcul  aux  fonctions  irrationelles 
en  se  debarrassant  des  irrationalites  par  1'elevation 
des  radicaux  aux  puissances."    This  is  at  once  giv- 
ing up  the  point  in  question.     It  is  allowing  une- 
quivocally that  Fermat  in  these  processes  only  took 
a  circuitous  route  to  avoid  a  difficulty  which  it  is 
one  of  the  most  express  objects  of  the  differential 
calculus  to  face  and  surmount.    The  whole  claim 
of  the  French  geometer  arises  from  a  confusion  (too 
often  made)  of  the  calculus  and  its  applications,  the 
means  and  the  end,  under  the  sweeping  head  of 

*  nouveaux  calculs'  on  the  one  hand,  and  an  asser- 
tion  somewhat  too  unqualified,   advanced   in  the 
warmth  and  generality  of  a  preface,  on  the  other."* 

The  discoveries  of  Fermat  were  improved  and 
simplified  by  Hudde,  Huygens,  and  Barrow ;  and  by 
the  publication  of  the  Arithmetic  of  Infinites  by  Dr. 
Wallis,  Savilian  professor  of  geometry  at  Oxford, 
mathematicians  were  conducted  to  the  very  entrance 
of  a  new  and  untrodden  field  of  discovery.  This 
distinguished  author  had  effected  the  quadrature  of 
all  curves  whose  ordinates  can  be  expressed  by  any 
direct  integral  powers ;  and  though  he  had  extended 
his  conclusions  to  the  cases  where  the  ordinates  are 
xpressed  by  the  inverse  or  fractional  powers,  yet 

*  Art.  Mathematics,  in  the  Edinburgh  Encyclopaedia,  volume  xiii. 
p.  365. 


ARITHMETIC    OF   INFINITES.  173 

ie  failed  in  its  application.  Nicolas  Mercator  (Kauff- 
tian)  surmounted  the  difficulty  by  which  Wallis 
nad  been  baffled,  by  the  continued  division  of  the 
numerator  by  the  denominator  to  infinity,  and  then 
applying  Wallis's  method  to  the  resulting  positive 
Bowers.  In  this  way  he  obtained,  in  1667,  the  first 
general  quadrature  of  the  hyperbola,  and,  at  the 
ame  time,  gave  the  regular  development  of  a  func- 
ion  in  series. 

In  order  to  obtain  the  quadrature  of  the  circle,  Dr. 
Vallis  considered  that  if  the  equations  of  the  curves 
f  which  he  had  given  the  quadrature  were  arranged 
i  a  series,  beginning  with  the  most  simple,  these 
reas  would  form  another  series.     He  saw  also  that 
tie  equation  of  the  circle  was  intermediate  between 
he  first  and  second  terms  of  the  first  series,  or 
etween  the  equation  of  a  straight  line  and  that  of 
parabola,  and  hence  he  concluded,  that  by  interpo- 
ating  a  term  between  the  first  and  second  term  of 
be  second  series,  he  would  obtain  the  area  of  the 
ircle.     In  pursuing  this  singularly  beautiful  thought, 
Dr.  Wallis  did  not  succeed  in  obtaining  the  indefinite 
quadrature  of  the  circle,  because  he  did  not  employ 
(general  exponents;  but  he  was  led  to  express  the 
entire  area  of  the  circle  by  a  fraction,  the  numerator 
and  denominator  of  which  are  each  obtained  by 
the  continued  multiplication  of  a  certain  series  of 
numbers. 

Such  was  the  state  of  this  branch  of  mathematical 
science,  when  Newton,  at  an  early  age,  directed  to 
it  the  vigour  of  his  mind.  At  the  very  beginning 
of  his  mathematical  studies,  when  the  works  of  Dr. 
Wallis  fell  into  his  hands,  he  was  led  to  consider 
how  he  could  interpolate  the  general  values  of  the 
areas  in  the  second  series  of  that  mathematician. 
With  this  view  he  investigated  the  arithmetical  law 
of  the  coefficients  of  the  series,  and  obtained  a 
general  method  of  interpolating,  not  only  the  series 
above  referred  to,  but  also  other  series.  These 
P2 


174  SIR   ISAAC   NEWTON. 

were  the  first  steps  taken  by  Newton,  and,  as  he 
himself  informs  us,  they  would  have  entirely  escaped 
from  his  memory  if  he  had  not,  a  few  weeks 
before,*  found  the  notes  which  he  made  upon  the 
subject.  When  he  had  obtained  this  method,  it  oc- 
curred to  him  that  the  very  same  process  was  appli- 
cable to  the  ordinates,  and,  by  following  out  this 
idea,  he  discovered  the  general  method  of  reducing 
radical  quantities  composed  of  several  terms  into 
infinite  series,  and  was  thus  led  to  the  discovery  of 
the  celebrated  Binomial  Theorem.  He  now  neglected 
entirely  his  methods  of  interpolation,  and  employed 
that  theorem  alone  as  the  easiest  and  most  direct 
method  for  the  quadratures  of  curves,  and  in  the  solu- 
tion of  many  questions  which  had  not  even  been 
attempted  by  the  most  skilful  mathematicians. 

After  having  applied  the  Binomial  theorem  to  the 
rectification  of  curves,  and  to  the  determination  of 
the  surfaces  and  contents  of  solids,  and  the  position 
of  their  centres  of  gravity,  he  discovered  the  general 
principle  of  deducing  the  areas  of  curves  from  the 
Vjyrdinate,  by  considering  the  area  as  a  nascent  quan- 
tity, increasing  by  continual  fluxion  in  the  propor- 
tion of  the  length  of  the  ordinate,  and  supposing 
the  abscissa  to  increase  uniformly  in  proportion  to 
the  time.  In  imitation  of  Cavalerius,  he  called  the 
momentary  increment  of  a  line  a  point,  though  it  is 
not  a  geometrical  point,  but  an  infinitely  short  line ; 
and  the  momentary  increment  of  an  area  or  surface 
he  called  a  line,  though  it  is  not  a  geometrical  line, 
but  an  infinitely  narrow  surface.  By  thus  regarding 
lines  as  generated  by  the  motion  of  points,  surfaces 
by  the  motions  of  lines,  and  solids  by  the  motion  of 
surfaces,  and  by  considering  that  the  ordinates,  ab- 
scissae, &c.  of  curves  thus  formed,  vary  according 
to  a  regular  law  depending  on  the  equation  of  the 

*  These  facts  are  mentioned  in  Newton's  letter  to  Oldenburgh,  Octo» 
ber  24, 1676. 


DOCTRINE  OF  FLUXIONS.         173 

:urve.  he  deduces  from  this  equation  the  velocities 
.vith  which  these  quantities  are  generated ;  and  by 
;he  rules  of  infinite  series  he  obtains  the  ultimate 
/alue  of  the  quantity  required.  To  the  velocities 
Sivith  which  every  line  or  quantity  is  generated, 
LVevvton  gave  the  name  of  Fluxions,  and  to  the  lines 
or  quantities  themselves  that  of  Fluents.  This 
nethod  constitutes  the  doctrine  of  fluxions  v^hich 
Newton  had  invented  previous  to  1666,  when  the 
Breaking  out  of  the  plague  at  Cambridge  drove  him 
Tom  that  city,  and  turned  his  attention  to  other 
subjects. 

But  though  Newton  had  not  communicated  this 
invention  to  any  of  his  friends,  he  composed 
ilis  treatise,  entitled  Analysis  per  equationes  numero 
terminorum  infinitas,  in  which  the  principle  of  fluxions 
and  its  numerous  applications  are  clearly  pointed 
out.  In  the  month  of  June,  1669,  he  communicated 
his  work  to  Dr.  Barrow,  who  mentions  it  in  a  letter 
o  Mr.  Collins,  dated  the  20th  June,  1669,  as  the  pro- 
duction of  a  friend  of  his  residing  at  Cambiidge,  who 
possesses  a  fine  genius  for  such  inquiries.  On  the 
1st  July,  he  transmitted  the  work  to  Collins;  and 
laving  received  his  approbation  of  it,  he  informs  him 
;hat  the  name  of  the  author  of  it  was  Newton,  a 
ellow  of  his  own  college,  and  a  young  man  who 
lad  only  two  years  before  taken  his  degree  of  M.A. 
ollins  'took  a  copy  of  this  treatise,  and  returned  the 
original  to  Dr.  Barrow ;  and  this  copy  having  been 
bund  among  Collins's  papers  by  his  friend  Mr.  Wil- 
iam  Jones,  and  compared  with  the  original  manu- 
cript  Arrowed  from  Newton,  it  was  published  with 
he  coHsent  of  Newton  in  1711,  nearly  fifty  years 
after  it  was  written. 

Though  the  discoveries  contained  in  this  treatise 
were  not  at  first  given  to  the  world,  yet  they  were 
made  generally  known  to  mathematician,  by  the 
correspondence  of  Collins,  who  communicated  them 
to  James  Gregory;  to  MM.  Bertet  and  Vernon  in 


176  SIR   ISAAC   NEWTON. 

France;  to  Slusius  in  Holland;  to  Borelli  in  Italy? 
and  to  Strode,  Townsend,  and  Oldenburg,  in  letter* 
dated  between  1669  and  1672. 

Hitherto  the  method  of  fluxions  was  known  only 
to  the  friends  of  Newton  and  their  correspondents ; 
but,  in  the  first  edition  of  the  Principia,  which  ap- 
peared in  1687,  he  published,  for  the  first  time,  the 
^  fundamental  principle  of  the  fluxionary  calculus,  in 
the  second  lemma  of  the  second  book.  No  infor- 
mation, however,  is  here  given  respecting  the  algo- 
rithm or  notation  of  the  calculus ;  and  it  was  not  till 
1693-5[?]  that  it  was  communicated  to  the  mathemat- 
ical world  in  the  second  volume  of  Dr.  Wallis's  works, 
which  were  published  in  that  year.  This  informa- 
tion was  extracted  from  two  letters  of  Newton 
written  in  1692. 

About  the  year  1672,  Newton  had  undertaken  to 
publish  an  edition  of  Kinckhuysen's  Algebra,  with 
notes  and  additions.  He  therefore  drew  up  a  trea- 
tise, entitled,  A  Method  of  Fluxions,  which  he  pro- 
posed as  an  introduction  to  that  work ;  but  the  fear 
of  being  involved  in  disputes  about  this  new  dis- 
covery, or  perhaps  the  wish  to  render  it  more  com- 
plete, or  to  have  the  sole  advantage  of  employing 
it  in  his  physical  researches,  induced  him  to  abandon 
this  design.  At  a  later  period  of  his  life  he  again 
resolved  to  give  it  to  the  world ;  but  it  did  not  ap- 
pear till  after  his  death,  when  it  was  translated  into 
English,  and  published  in  1736,  with  a  commentary 
by  Mr.  John  Colson,  Professor  of  Mathematics  in 
Cambridge.* 

To  the  first  edition  of  Newton's  Optics^g^hich 
appeared  in  1704,  there  were  added  two  mathematical 

*  Dr.  Pomberton  informs  us  that  he  had  prevailed  upon  Sir  Isaac  to 
publish  this  treatise  during  his  lifetime,  and  that  he  had  for  this  purpose 
examined  all  the  calculations  and  prepared  part  of  the  figures.  But  as 
the  latter  part  of  the  treatise  had  never  been  finished,  Sir  Isaac  was 
about  to  let  him  have  other  papers  to  supply  what  was  wanting,  when 
his  death  put  a  stop  to  the  plan.—Preface  to  Pemberton's  View  qf  Sir 
Isaac  Newton's  Philosophy 


DOCTRINF  OF  FLUXIONS.          177 

realises,  entitled,  Tractatus  duo  de  speciebus  et  mag- 
ittudine  figurarum  curvilinearum,  the  one  bearing  the 
itle  of  Tractatus  de  Quadraiura  Curvarum,  and  the 
)ther  Enumeratio  linjarum  tertii  ordinis.  The  first 
;ontains  an  explanation  of  the  doctrine  of  fluxions, 
ind  of  its  application  to  the  quadrature  of  curves ; 
md  the  second  a  classification  of  seventy-two  curves 
)f  the  third  order,  with  an  account  of  their  proper- 
ies.  The  reason  for  publishing  these  two  tracts  in 
lis  Optics  (in  the  subsequent  editions  of  which  they 
ire  omitted)  is  thus  stated  in  the  advertisement : — 

In  a  letter  written  to  M.  Leibnitz  in  the  year  1679, 
ind  published  by  Dr.  Wallis,  I  mentioned  a  method 
>y  which  I  had  found  some  general  theorems  about 
squaring  curvilinear  figures  on  comparing  them  with 
he  conic  sections,  or  other  the  simplest  figures  with 
vhich  they  might  be  compared.  And  some  years 
igo  I  lent  out  a  manuscript  containing  such  theo- 
•ems ;  and  having  since  met  with  some  things  copied 
>ut  of  it,  I  have  on  this  occasion  made  it  public,  pre- 
ixing  to  it  an  introduction,  and  joining  a  scholium 
3oncerning  that  method.  And  I  have  joined  with  it 
mother  small  tract  concerning  the  curvilineal  figures 
the  second  kind,  which  was  also  written  many 
fears  ago,  and  made  known  to  some  friends,  who 
lave  solicited  the  making  it  public." 

In  the  year  1707,  Mr.  Whiston  published  the  alge- 
)raical  lectures  which  Newton  had,  during  nine  years, 
delivered  at  Cambridge,  under  the  title  of  Arithmetica 
Universalis,  sive  de  Compositions  et  Resolutions  Arith- 
inetica  Liber.  We  are  not  accurately  informed  how 
Mr.  Whiston  obtained  pr  osession  of  this  work ;  but 
it  is  stated  by  one  of  the  editors  of  the  English 
edition,  that  "  Mr.  Whiston  thinking  it  a  pity  that  so 
noble  and  useful  a  work  should  be  doomed  to  a  col- 
lege confinement,  obtained  leave  to  make  it  public." 
It  was  soon  afterward  translated  into  English  by 
Mr.  Ralphson ;  and  a  second  edition  of  it,  with  im- 
provements by  the  author,  was  published  at  London 


178  SIR   ISAAC   NEWTON. 

in  1712,  by  Dr.  Maclim,  secretary  to  the  Royal 
ciety.  With  the  view  of  stimulating  mathematicians 
1o  write  annotations  on  this  admirable  work,  the 
celebrated  S'Gravesande  published  a  tract,  entitled, 
Specimen  Commentarii  in  Arithmeticam  Universalem ; 
and  Maclaurin's  Algebra  seems  to  have  been  drawn 
up  in  consequence  of  this  appeal. 

Among  the  mathematical  works  of  Newton  we 
must  not  omit  to  enumerate  a  small  tract  entitled, 
Methodus  Differ  entialis,  which  was  published  with 
his  consent  in  1711.  It  consists  of  six  propositions,, 
which  contain  a  method  of  drawing  a  parabolic  curv^ 
through  any  given  number  of  points,  and  which  arer 
useful  for  constructing  tables  by  the  interpolation  of; 
series,  and  for  solving  problems  depending  on  the 
quadrature  of  curves. 

Another  mathematical  treatise  of  Newton's  was 
published  for  the  first  time  in  1779,  in  Dr.  Horsley's 
edition  of  his  works.*  It  is  entitled,  Artis  Analytics 
Specimina,  vel  Geometria  Analylica.  In  editing  this 
work,  which  occupies  about  130  quarto  pages,  Dr. 
Horsley  used  three  manuscripts,  one  of  which  was 
in  the  handwriting  of  the  author ;  .another,  written; 
in  an  unknown  hand,  was  given  by  Mr.  William: 
Jones  to  the  Honourable  Charles  Cavendish ;  and  a 
third,  copied  from  this  by  Mr.  James  Wilson,  the 
.editor  of  Robins's  works,  was  given  to  Dr.  Horsley 
by  Mr.  John  Nourse,  bookseller  to  the  king.  Dr. 
Horsley  has  divided  it  into  twelve  chapters,  which; 
treat  of  infinite  series ;  of  the  reduction  of  affected 
equations;  of  the  specious  resolution  of  equations; 
of  the  doctrine  of  fluxions;  of  maxima  and  minima; 
of  drawing  tangents  to  curves ;  of  the  radius  of  cur* 
vature  ;  of  the  quadrature  of  curves ;  of  the  area  of 
curves  which  are  comparable  with  the  conic  sec* 
tions ;  of  the  construction  of  mechanical  problems; 
and  on  finding  the  lengths  of  curves. 

*  IsEci  Newtoni  Opera  quae  extant  omnia,  vol.  i.  p.  38S-519. 


SOLUTION  OF  PROBLEMS.         179 

In  enumerating  the  mathematical  works  of  our 
rathor,  we  must  not  overlook  his  solutions  of  the 
celebrated  problems  proposed  by  Bernouilli  and 
Leibnitz.  On  the  Kalends  of  January,  1697,  John 
3ernouilli  addressed  a  letter  to  the  most  distin- 
guished mathematicians  in  Europe,f  challenging 
hem  to  solve  the  two  following  problems : 

1.  To  determine  the  curve  line  connecting  two 
ven  points  which  are  at  different  distances  from 

he  horizon,  and  not  in  the  same  vertical  line,  along 
hich  a  body  passing  by  its  own  gravity,  and  begin- 
ing  to  move  at  the  upper  point,  shall  descend  to  the 

ower  point  in  the  shortest  time  possible. 

2.  To  find  a  curve  line  of  this  property  that  the 
wo  segments  of  a  right  line  drawn  from  a  given 
oint  through  the  curve,  being  raised  to  any  given 
ower,  and  taken  together,  may  make  every  where 
tie  same  sum. 

On  the  day  after  he  received  these  problems, 
Newton  addressed  to  Mr.  Charles  Montague,  the 
^resident  of  the  Royal  Society,  a  solution  of  them 
oth.  He  announced  that  the  curve  required  in  the 
rst  problem  must  be  a  cycloid,  and  he  gave  a 
nethod  of  determining  it.  He  solved  also  the 
econd  problem,  and  he  showed  that  by  the  same 
method  other  curves  might  be  found  which  shall  cut 
ff  three  or  more  segments  having  the  like  proper- 
es.  Leibnitz,  who  was  struck  with  the  beauty  of 
le  problem,  requested  Bernouilli,  who  had  allowed 
ix  months  for  its  solution,  to  extend  the  period  to 
welve  months.  This  delay  was  readily  granted, 
olutions  were  obtained  from  Newton,  Leibnitz,  and 
Marquis  de  L'Hopital ;  and  although  that  of 
Newton  was  anonymous,  yet  Bernouilli  recognised 

it  his  powerful  mind,  "  tanquam?  says  he,  "  ex 
ngue  leonem"  as  the  lion  is  known  by  his  claw. 

The  last  mathematical  effort  of  our  author  was 

*  "  Acutissimis  aui  toto  orbe  florent  Mathematicis." 


(180  SIR  ISAAC   NEWTON. 

made  with  his  usual  success,  in  solving  a  problem 
which  Leibnitz  proposed  in  1716,  in  a  letter  to  the 
Abbe  Conti,  "  for  the  purpose,  as  he  expressed  it 
of  feeling  the  pulse  of  the  English  analysts."    The 
object  of  this  problem  was  to  determine  the  curve 
which  should  cut  at  right  angles  an  infinity  of  curves 
of  a  given  nature,  but  expressible  by  the  same  equa- 
tion.    Newton  received  this  problem   about   five 
o'clock  in  the  afternoon,  as  he  was  returning  from 
the  Mint;  and  though  the  problem  was  extremely, 
difficult,  and  he  himself  much  fatigued  with  business,* 
yet  he  finished  the  solution  of  it  before  he  wenk 
to  bed. 

Such  is  a  brief  account  of  the  mathematical  writ- 
ings of  Sir  Isaac  Newton,  not  one  of  which  were 
voluntarily  communicated  to  the  world  by  himself, 
The  publication  of  his  Universal  Arithmetic  is  said 
to  have  been  a  breach  of  confidence  on  the  part  of 
Whiston ;  and,  however  this  may  be,  it  was  an  un- 
finished work,  never  designed  for  the  public.  The 
publication  of  his  Quadrature  of  Curves,  and  of  hii, 
Enumeration  of  Curve  Lines,  was  rendered  neces* 
sary,  in  consequence  of  plagiarisms  from  the  manu* 
scripts  of  them  which  he  had  lent  to  his  friends,  and 
the  rest  of  his  analytical  writings  did  not  appear  till 
after  his  death.  It  is  not  easy  to  penetrate  into  the 
motives  by  which  this  great  man  was  on  these 
occasions  actuated.  If  his  object  was  to  keep  pos- 
session of  his  discoveries  till  he  had  brought  them 
to  a  higher  degree  of  perfection,  we  may  approve  of 
the  propriety,  though  we  cannot  admire  the  prudence 
of  such  a  step.  If  he  wished  to  retain  to  himself 
his  own  methods,  in  order  that  he  alone  might  have 
the  advantage  of  them  in  prosecuting  his  physical 
inquiries,  we  cannot  reconcile  so  selfish  a  measure 
with  that  openness  and  generosity  of  character 
which  marked  the  whole  of  his  life.  If  he  withheld 
his  labours  from  the  world  in  order  to  avoid  the  dis~ 
putes  and  contentions  to  which  they  might  give  rise, 


HISTORY    OF    FLUXIONS.  181 

[opted  the  very  worst  method  of  securing  his 
iquillity.  That  this  was  the  leading  motive  under 
ch  he  acted,  there  is  little  reason  to  doubt.  The 
arty  delay  in  the  publication  of  his  method  of.  flux- 
ons,  after  the  breaking  out  of  the  plague  at  Cam- 
Bridge,  was  probably  owing  to  his  not  having  com- 
peted the  algorithm  of  that  calculus ;  but  no  apology 
:an  be  made  for  the  imprudence  of  withholding  it 
my  longer  from  the  public.  Had  he  published  this 
loble  discovery  even  previous  to  1673,  when  his 
preat  rival  had  not  even  entered  upon  those  studies 
tvhich  led  him  to  the  same  method,  he  would  have 
>ecured  to  himself  the  undivided  honour  of  the 
nvention,  and  Leibnitz  could  have  aspired  to  no  other 
ame  but  that  of  an  improver  of  the  doctrine  of  flux- 
ons.  But  he  unfortunately  acted  otherwise.  He 
Announced  to  his  friends  that  he  possessed  a  method 
}f  great  generality  and  power ;  he  communicated  to 
hem  a  general  account  of  its  principles  and  applica- 
ions  ;  and  the  information  which  was  thus  conveyed 
lirected  the  attention  of  mathematicians  to  subjects 
o  which  they  might  not  have  otherwise  applied  their 
Dowers.  In  this  way  the  discoveries  which  he  had 
previously  made  were  made  subsequently  by  others ; 
and  Leibnitz,  in  place  of  appearing  in  the  theatre  of 
cience  as  the  disciple  and  the  follower  of  Newton, 
tood  forth  with  all  the  dignity  of  a  rival ;  and,  by 
he  early  publication  of  his  discoveries  had  nearly 
placed  himself  on  the  throne  which  Newton  was 
destined  to  ascend. 

It  would  be  inconsistent  with  the  popular  nature 
of  a  work  like  this,  to  enter  into  a  detailed  history 
of  the  dispute  between  Newton  and  Leibnitz  re- 
specting the  invention  of  fluxions.  A  brief  and 
general  account  of  it,  however,  is  indispensable. 

In  the  beginning  of  1673,  Leibnitz  came  to  London 

in  the  suite  of  the  Duke  of  Hanover,  and  he  became 

acquainted  with  the  great  men  who  then  adorned 

the  capital  of  England.    Among  these  was  Olden- 

Q 


182  SBR   ISAAC   NEWTON. 

burg,  a  countryman  of  his  own,  who  was  then  sec- 
retary to  the  Royal  Society.  About  the  beginning 
of  March,  in  the  same  year,  Leibnitz  went  to  Paris, 
where,  with  the  assistance  of  Huygens,  he  devoted 
himself  to  the  study  of  the  higher  geometry.  In 
the  month  of  July  he  renewed  his  correspondence 
with  Oldenburg,  and  he  communicated  to  him  some  of 
the  discoveries  which  he  had  made  relative  to  series, 
particularly  the  series  for  a  circular  arc  in  terms  of 
the  tangent.  Oldenburg  informed  him  in  return  of 
the  discoveries  on  series  which  had  been  made  by 
Newton  and  Gregory ;  and  in  1676  Newton  commu- 
nicated to  him,  through  Oldenburg,  a  letter  of  fifteeE 
closely  printed  quarto  pages,  containing  many  of  his 
analytical  discoveries,  and  stating  that  he  possessed 
a  general  method  of  drawing  tangents,  which  he 
thought  it  necessary  to  conceal  in  two  sentences  of 
transposed  characters.  In  this  letter  neither  the 
method  of  fluxions  nor  any  of  its  principles  are 
communicated ;  but  the  superiority  of  the  method 
over  all  others  is  so  fully  described,  that  Leibnitz 
could  scarcely  fail  to  discover  that  Newton  pos- 
sessed that  secret  of  which  geometers  had  so  long 
been  in  quest. 

Had  Leibnitz  at  the  time  of  receiving  this  Icttei 
been  entirely  ignorant  of  his  own  differential  method, 
the  information  thus  conveyed  to  him  by  Newton 
could  not  fail  to  stimulate  his  curiosity,  and  excite 
his  mightiest  efforts  to  obtain  possession  of  so  great 
a  secret.  That  this  new  method  was  intimately 
connected  with  the  subject  of  series  was  clearly  in- 
dicated by  Newton;  and  as  Leibnitz  was  deeply 
versed  in  this  branch  of  analysis,  it  is  far  from  im- 
probable that  a  mind  of  such  strength  and  acuteness 
might  attain  his  object  by  direct  investigation.  That 
this  was  the  case  may  be  inferred  from  his  letter  to 
Oldenburg  (to  be  communicated  to  Newton)  of  the 
21st  June,  1677,  where  he  mentions  that  he  had  for 
some  time  been  in  possession  of  a  method  of  draw- 


HISTORY    OF   FLUXIONS.  183 

ng  tangents  more  general  than  that  of  Slusius, 
lamely,  by  the  differences  of  ordinates.  He  then 
Droceeds  with  the  utmost  frankness  to  explain  this 
nethod,  which  was  no  other  than  th^.  differential 
3alculus.  He  describes  the  algorithm  which  he  had 
idopted,  the  formation  of  differential  equations,  and 
he  application  of  the  calculus  to  various  geometrical 
and  analytical  questions.  No  answer  seems  to  have 
:>een  returned  to  this  letter  either  by  Newton  or 
Oldenburg,  and,  with  the  exception  of  a  short  letter 
rom  Leibnitz  to  Oldenburg,  dated  12th  July,  1677, 
10  further  correspondence  seems  to  have  taken 
)lace.  This,  no  doubt,  arose  from  the  death  of  Ol- 
denburg in  the  month  of  August,  1677,*  when  the 
wo  rival  geometers  pursued  their  researches  with 
ill  the  ardour  which  the  greatness  of  the  subject 
Was  so  well  calculated  to  inspire. 

In  the  hands  of  Leibnitz  the  differential  calculus 
nade  rapid  progress.  In  the  Acta  Eruditorum,  which 
>vas  published  at  Leipsic  in  November,  1684,  he  gave 
tie  first  account  of  it,  describing  its  algorithm  in  the 
ame  manner  as  he  had  done  in  his  letter  to  Olden- 
urg,  and  pointing  out  its  application  to  the  drawing 
f  tangents,  and  the  determination  of  maxima  and 
ninima.  He  makes  a  remote  reference  to  the  simi« 
ar  calculus  of  Newton,  but  lays  no  claim  to  the  sole 
avention  of  the  differential  method.  In  the  same 
vork  for  June,  1686,  he  resumes  the  subject ;  and 
vhen  Newton  had  not  published  a  single  word  upon 

*  Henry  Oldenburg,  whose  name  is  so  intimately  associated  with  the 
history  of  Newton's  discoveries,  was  born  at  Bremen,  and  was  consul 
from  that  town  to  London  during  the  usurpation  of  Cromwell.  Having 
lost  his  office,  and  being  compelled  to  seek  the  means  of  subsistence,  he 
became  tutor  to  an  English  nobleman,  whom  he  accompanied  to  Oxford 
in  1656.  During  his  residence  in  that  city  he  became  acquainted  with 
the  philosophers  who  established  the  Royal  Society,  and  upon  the  death 
of  William  Crown,  the  first  secretary,  he  was  appointed  in  1663,  joint 
secretary  along  with  Mr.  Wilkins.  He  kept  up  an  extensive  correspond- 
ence with  the  philosophers  of  all  nations,  and  he  was  the  author  of  sev- 
eral papers  in  the  Philosophical  Transactions,  and  of  some  works  which 
have  not  acquired  much  celebrity.  He  died  at  Charlton,  near  Greea 
wieh,  in  August,  1677. 


184  SIR   ISAAC    NEWTON. 

fluxions,  and  had  not  even  made  known  his  notation 
the  differential  calculus  was  making  rapid  advance: 
on  the  Continent,  and  in  the  hands  of  James  anc 
John  Bernouilli  had  proved  the  means  of  solving 
some  of  the  most  important  and  difficult  problems. 
The  silence  of  Newton  was  at  last  broken,  and  ir 
the  second  lemma  of  the  second  book  of  the  Prin- 
cipia,  he  explained  the  fundamental  principle  of  the 
fluxionary  calculus.  His  explanation,  which  occu- 
pied only  three  pages,  was  terminated  with  the  fol- 
lowing scholium: — "In  a  correspondence  which 
took  place  about  ten  years  ago  between  that  very 
skilful  geometer,  G.  G.  Leibnitz,  and  myself,  I  an- 
nounced to  him  that  I  possessed  a  method  of  deter- 
mining maxima  and  minima,  of  drawing  tangents, 
and  of  performing  similar  operations  which  was 
equally  applicable  to  rational  and  irrational  quanti- 
ties, and  concealed  the  same  in  transposed  letters 
involving  this  sentence,  (data  equations  quotcunque 
fluentes  quantitates  involvente^  fluxiones  invenire  et  vice 
versa).  This  illustrious  man  replied  that  he  also 
had  fallen  on  a  method  of  the  same  kind,  and  he 
communicated  to  me  his  method  which  scarcely 
differed  from  mine  except  in  the  notation  [and  in  the 
idea  of  the  generation  of  quantities."]*  This  cele- 
brated scholium,  which  is  so  often  referred  to  in  the 
present  controversy,  has,  in  our  opinion,  been  much 
misapprehended.  While  M.  Biot  considers  it  as 
"  eternalizing  the  rights  of  Leibnitz  by  recognising 
them  in  the  Principia,"  Professor  Playfair  regards  it 
as  containing  "  a  highly  favourable  opinion  on  the 
subject  of  the  discoveries  of  Leibnitz."  To  us  it 
appears  to  be  nothing  more  than  the  simple  state- 
ment of  the  fact,  that  the  method  communicated  by 
Leibnitz  was  nearly  the  same  as  his  own ;  and  this 
much  he  might  have  said,  whether  he  believed  that 
Leibnitz  had  seen  the  fluxionary  calculus  among  the 

*  These  words  in  brackets  are  in  the  second  edition,  but  not  in  the  first. 


HISTORY    OF    FLUXIONS.  185 

>apers  of  Collins,  or  was  the  independent  inventor 
>f  his  own.  It  is  more  than  probable,  indeed,  that 
vhen  Newton  wrote  this  scholium  he  regarded 
bnitz  as  a  second  inventor ;  but  when  he  found 
hat  Leibnitz  and  his  friends  had  showed  a  willing- 
tess  to  believe,  and  had  even  ventured  to  throw  out 
he  suspicion,  that  he  himself  had  borrowed  the  doc- 
jine  of  fluxions  from  the  differential  calculus,  he 
eems  to  have  altered  the  opinion  which  he  had 
ormed  of  his  rival,  and  to  have  been  willing  in  his 
urn  to  retort  the  charge. 

This  change  of  opinion  was  brought  about  by  a 
eries  of  circumstances  over  which  lie  had  no  con- 
rol.  M.  Nicolas  Fatio  de  Duillier,  a  Swiss  mathe- 
natician,  resident  in  London,  communicated  to  the 
loyal  Society,  in  1699,  a  paper  on  the  line  of  quick- 
st  descent,  which  contains  the  following  observa- 
ions : — "  Compelled  by  the  evidence  of  facts,  I  hold 
Vewton  to  have  been  the  first  inventor  of  this  cal- 
ulus,  and  the  earliest  by  several  years ;  and  whether 
^eibnitz,  the  second  inventor,  has  borrowed  any  thing' 
rom  the  other,  I  would  prefer  to  my  own  judgment 
hat  of  those  who  have  seen  the  letters  and  other 
opies  of  the  same  manuscripts  of  Newton."  This 
mprudent  remark,  which  by  no  means  amounts  to  a 
harge  of  plagiarism,  for  Leibnitz  is  actually  desig- 
tated  the  second  inventor,  may  be  considered  as 
howing  that  the  English  mathematicians  had  been 
herishing  suspicions  unfavourable  to  Leibnitz,  and 
here  can  be  no  doubt  that  a  feeling  had  long  pre- 
vailed that  this  mathematician  either  had,  or  might 
lave  seen,  among  the  papers  of  Collins,  the  u  Analy- 
is  per  Equationes,  fyc.?  which  contained  the  prin- 
.iples  of  the  fluxionary  method.  Leibnitz  replied  to 
he  remark  of  Duillier  with  much  good  feeling. 
le  appealed  to  the  facts  as  exhibited  in  his  corres- 
pondence with  Oldenburg ;  he  referred  to  Newton's 
scholium  as  a  testimony  in  his  favour ;  and,  without 
disDuting  or  acknowledging  the  priority  of  Newton's 


186  SIR  ISAAC   NEWTON. 

claim,  he  asserted  his  own  right  to  the  invention  of 
the  differential  calculus .  Fatio  transmitted  a  reply  to 
the  Leipsic  Acts  ;  but  the  editor  refused  to  insert  it. 
The  dispute,  therefore,  terminated,  and  the  feelings 
of  the  contending  parties  continued  for  some  time 
in  a  state  of  repose,  though  ready  to  break  out  on 
the  slightest  provocation. 

When  Newton's  Optics  appeared  in  1704,  accom- 
panied by  his  Treatise  on  the  Quadrature  of  Curves, 
and  his  enumeration  of  lines  of  the  third  order,  the 
editor  of  the  Leipsic  Acts  (whom  Newton  supposed 
to  be  Leibnitz  himself)  took  occasion  to  review  the 
first  of  these  tracts.  After  giving  an  imperfect 
analysis  of  its  contents,  he  compared  the  method 
of  fluxions  with  the  differential  calculus,  and,  in  a 
sentence  of  some  ambiguity,  he  states  that  Newton 
employed  fluxions  in  place  of  the  differences  of  Leib- 
nitz, and  made  use  of  them  in  his  Principia  in  the 
same  manner  as  Honoratus  Fabri,  in  his  Synopsis 
of  Geometry,  had  substituted  progressive  motion  in 
place  of  the  indivisibles  of  Cavaleri.*  As  Fabri, 
therefore,  was  not  the  inventor  of  the  method 
which  is  here  referred  to,  but  borrowed  it  from  Ca- 
valeri, and  only  changed  the  mode  of  its  expression, 
there  can  be  no  doubt  that  the  artful  insinuation 
contained  in  the  above  passage  was  intended  to  con- 
vey the  impression  that  Newton  had  stolen  his  me- 
thod of  fluxions  from  Leibnitz.  The  indirect  char- 
acter of  this  attack,  in  place  of  mitigating  its  severity, 
renders  it  doubly  odious ;  and  we  are  persuaded  that 
no  candid  reader  can  peruse  the  passage  without  a 
strong  conviction  that  it  justifies,  in  the  fullest  man- 

r  *  As  this  passage  is  of  essential  importance  in  this  controversy,  we 
shall  give  it  in  the  original.  "  Pro  dijferentiis  igitur  Leibnitianis  D. 
Newtonus  adhibet,  semper que  adhibuit^JluxioneSj  quee  sunt  quam  prox- 
ime  ut  fluentium  augmenta,  sequalibus  temporis  particulis  quam  mini- 
mis  genita ;  iisque  tarn  in  suis  Principiis  Naturae  Mathematicis,  turn  in 
aliis  postea  editis,  elegantcr  est  usus ;  quern  admodum  et  Honoratus 
Fabrius  in  sua  Synopsi  Geometrica,  motuumque  progressus  Cavalle- 
riancs  methodo  siibstituit." 


HISTORY   OF   FLUXIONS.  187 

aer,  the  indignant  feelings  which  it  excited  among 
the  English  philosophers.    If  Leibnitz  was  the  author 
of  the  review,  or  if  he  was  in  any  way  a  party  to  it, 
he  merited  the  full  measure  of  rebuke  which  was 
dealt  out  to  him  by  the  friends  of  Newton,  and  de- 
served those  severe  reprisals  which  doubtless  im- 
bittered  the  rest  of  his  days.     He  who  dared  to  ac- 
!  cuse  a  man  like  Newton,  or  indeed  any  man  holding 
a  fair  character  in  society,  with  the  odious  crime  of 
;  plagiarism,  placed  himself  without  the  pale  of  the 
ordinary  courtesies  of  life,  and  deserved  to  have 
f  the  same  charge  thrown  back  upon  himself.     The 
,  man  who  conceives  his  fellow  to  be  capable  of  such 
intellectual  felony,  avows  the  possibility  of  himself 
I  committing  it,  and  almost  substantiates  the  weakest 
evidence  of  the  worst  accusers. 

Dr.  Keill,  as  the  representative  of  Newton's 
friends,  could  not  brook  this  base  attack  upon  his 
countryman.  In  a  letter  printed  in  the  Philosophi- 
cal Transactions  for  1708,  he  maintained  that  Newton 
was  "  beyond  all  doubt"  the  first  inventor  of  fluxions. 
He  referred  for  a  direct  proof  of  this  to  his  letters 
published  by  Wallis ;  and  he  asserted  "  that  the  same 
calculus  was  afterward  published  by  Leibnitz,  the 
name  and  the  mode  of  notation  being  changed-." 
If  the  reader  is  disposed  to  consider  this  passage 
as  retorting  the  charge  of  plagiarism  upon  Leibnitz, 
he  will  readily  admit  that  the  mode  of,  its  expres- 
sion is  neither  so  coarse  nor  so  insidious  as  that 
which  is  used  by  the  writer  in  the  Leipsic  Acts. 
In  a  letter  to  Hans  Sloane,  dated  March,  1711,  Leib- 
nitz complained  to  the  Royal  Society  of  the  treat- 
ment he  had  received.  He  expressed  his  conviction 
that  Keill  had  erred  more  from  rashness  of  judgment 
than  from  any  improper  motive,  and  that  he  did  not 
regard  the  accusation  as  a  calumny;  and  he  re- 
quested that  the  society  would  oblige  Mr.  Keill  to 
disown  publicly  the  injurious  sense  which  his  words 
might  bear.  When  this  letter  was  read  to  the 


188  «IR   ISAAC    NEWTON. 

society,  Keill  justified  himself  to  Sir  Isaac  Newton 
and  the  other  members  by  showing  them  the  ob- 
noxious review  of  the  Quadrature  of  Curves  in  the 
Leipsic  Acts.  They  all  agreed  in  attaching  the  same 
injurious  meaning  to  the  passage  which  we  formerly 
quoted,  and  authorized  Keill  to  explain  and  defend 
his  statement.  He  accordingly  addressed  a  letter 
to  Sir  Hans  Sloane,  which  was  read  at  the  society 
on  the  24th  May,  1711,  and  a  copy  of  which  was 
ordered  to  be  sent  to  Leibnitz.  In  this  letter,  which 
is  one  of  considerable  length,  he  declares  that  he 
never  meant  to  state  that  Leibnitz  knew  either  the 
name  of  Newton's  method  or  the  form  of  notation, 
and  that  the  real  meaning  of  the  passage  was,  "  that 
Newton  was  the  first  inventor  of  fluxions  or  of  the 
differential  calculus,  and  that  he  had  given,  in  two 
letters  to  Oldenburg,  and  which  he  had  transmitted 
to  Leibnitz,  indications  of  it  sufficiently  intelligible 
to  an  acute  mind,  from  which  Leibnitz  derived,  or  at 
least  might  derive,  the  principles  of  his  calculus." 

The  charge  of  plagiarism  which  Leibnitz  thought 
was  implied  in  the  former  letter  of  his  antagonist 
is  here  greatly  modified,  if  not  altogether  denied. 
Keill  expresses  only  an  opinion  that  the  letter  seen 
by  Leibnitz  contained  intelligible  indications  of  the 
fluxionary  calculus.  Even  if  this  opinion  were  cor- 
rect, it  is  no  proof  that  Leibnitz  either  saw  these  indi- 
cations or  availed  himself  of  them,  or  if  he  did  per- 
ceive them,  it  might  have  been  in  consequence  of  his 
having  previously  been  in  possession  of  the  differential 
calculus,  or  having  enjoyed  some  distant  view  of  it. 
Leibnitz  should,  therefore,  have  allowed  the  dispute 
to  terminate  here ;  for  no  ingenuity  on  his  part,  and 
no  additional  facts,  could  affect  an  opinion  which 
any  other  person  as  well  as  Keill  was  entitled  to 
maintain. 

Leibnitz,  however,  took  a  different  view  of  the 
subject,  and  wrote  a  letter  to  Sir  Hans  Sloane, 
dated  December  19, 1711,  which  excited  new  feelings, 


HISTORY   OF   FLUXIONS.  189 

and  involved  him  in  new  embarrassments.  Insensi- 
ble to  the  mitigation  which  had  been  kindly  impressed 
bpon  the  supposed  charge  against  his  honour,  he 
jalleges  that  Keill  had  attacked  his  candour  and  sin- 
scerity  more  openly  than  before; — that  he  acted 
(without  any  authority  from  Sir  Isaac  Newton,  who 
jwas  the  party  interested ; — and  that  it  was  in  vain 
to  justify  his  proceedings  by  referring  to  the  provo- 
cation in  the  Leipsic  Acts,  because  in  that  journal 
\no  injustice  had  been  done  to  any  party,  but  every  one 
\had  received  what  was  his  due.  He  branded  Keill  with 
Ithe  odious  appellation  of  an  upstart,  and  one  little 
acquainted  with  the  circumstances  of  the  case  ;*  he 
called  upon  the  society  to  silence  his  vain  and  un- 
just clamours,!  which,  he  believed,  were  disapproved 
by  Newton  himself,  who  was  well  acquainted  with 

te  facts,  and  who,  he  was  persuaded,  would  will- 
ingly give  his  opinion  on  the  matter. 

This  unfortunate  letter  was  doubtless  the  cause 
of  all  the  rancour  and  controversy  which  so  speedily 
followed,  and  it  placed  his  antagonist  in  a  new  and  a 
more  favourable  position.  It  may  be  correct,  thougfr 
few  will  admit  it,  that  Keill's  second  letter  was  more 
injurious  than  the  first;  but  it  was  not  true  that 
Keill  acted  without  the  authority  of  Newton,  be- 
muse KeilPs  letter  was  approved  of  and  trans- 
mitted by  the  Royal  Society,  of  which  Newton  was 
the  president,  and  therefore  became  the  act  of  that 
body.  The  obnoxious  part,  however,  of  Leibnitz's 
letter  consisted  in  his  appropriating  to  himself  the 
opinions  of  the  reviewer  in  the  Leipsic  Acts,  by 
declaring  that,  in  a  review  which  charged  Newton 
with  plagiarism,  every  person  had  got  what  was 
his  due.  The  whole  character  of  the  controversy 
was  now  changed :  Leibnitz  places  himself  in  the 


*  Homine  docto,  ged  novo,  et  parjim  perito  rerum  ante  actarum  cog 
nitare. 
t  Vanae  et  injustae  vociferationes. 


190  SIR   ISAAC   NEWTON. 

position  of  the  party  who  had  first  disturbed  the 
tranquillity  of  science  by  maligning  its  most  distin- 
guished ornament ;  and  the  Royal  Society  was  im- 
periously called  upon  to  throw  all  the  light  they 
could  upon  a  transaction  which  had  exposed  their 
venerable  president  to  so  false  a  charge.  The  so- 
ciety, too,  had  become  a  party  to  the  question,  by 
their  approbation  and  transmission  of  Keill's  second 
letter,  and  were  on  that  account  alone  bound  to  vin- 
dicate the  step  which  they  had  taken. 

When  the  letter  of  Leibnitz,  therefore,  was  read, 
Keill  appealed  to  the  registers  of  the  society  for; 
the  proofs  of  what  he  had  advanced ;  Sir  Isaac  also 
expressed  his  displeasure  at  the  obnoxious  passage 
in  the  Leipsic  Review,  and  at  the  defence  of  it  by 
Leibnitz,  and  he  left  it  to  the  society  to  act  as  they 
thought  proper.  A  committee  was  therefore  ap- 
pointed on  the  1 1th  March,  consisting  of  Dr.  Arbuth- 
not,  Mr.  Hill,  Dr.  Halley,  Mr.  Jones,  Mr.  Machin, 
and  Mr.  Burnet,  who  were  instructed  to  examine 
the  ancient  registers  of  the  society,  to  inquire  into 
the  dispute,  and  to  produce  such  documents  as  they 
should  find,  together  with  their  own  opinions  on  the 
subject.  On  the  24th  April  the  committee  produced 
the  following  report : — 

"  We  have  consulted  the  letters  and  letter-books 
in  the  custody  of  the  Royal  Society,  and  those 
found  among  the  papers  of  Mr.  John  Collins,  dated 
between  the  years  1669  and  1677,  inclusive ;  and 
showed  them  to  such  as  knew  and  avouched  the 
hands  of  Mr.  Barrow,  Mr.  Collins,  Mr.  Oldenburg, 
and  Mr.  Leibnitz;  and  compared  those  of  Mr. 
Gregory  with  one  another,  and  with  copies  of  some 
of  them  taken  in  the  hand  of  Mr.  Collins ;  and  have 
extracted  from  them  what  relates  to  the  matter  re- 
ferred to  us ;  all  which  extracts  herewith  delivered 
to  you  we  believe  to  be  genuine  and  authentic.  And 
by  these  letters  and  papers  we  find, — 

"  I.  Mr.  Leibnitz  was  in  London  in  the  beginning 


REPORT  OF  THE  ROYAL  SOCIETY.     191 

of  the  year  1673;  and  went  thence,  in  or  about 
March,  to  Paris,  where  he  kept  a  correspondence 
with  Mr.  Collins  by  means  of  Mr.  Oldenburg,  till 
about  September,  1676,  and  then  returned  by  London 
and  Amsterdam  to  Hanover :  and  that  Mr.  Collina 
was  very  free  in  communicating  to  able  mathema- 
ticians what  he  had  received  from  Mr.  Newton  and 
Mr.  Gregory. 

"  II.  That  when  Mr.  Leibnitz  was  the  first  time  in 
London,  he  contended  for  the  invention  of  another 
differential  method  properly  so  called ;  and,  notwith- 
standing that  he  was  shown  by  Dr.  Pell  that  it  was 
Newton's  method,  persisted  in  maintaining  it  to  be 
his  own  invention,  by  reason  that  he  had  found  it  by 
himself  without  knowing  what  Newton  had  done 
before,  and  had  much  improved  it.  And  we  find  no 
mention  of  his  having  any  other  differential  method 
than  Newton's  before  his  letter  of  the  21st  of  June, 
1677,  which  was  a  year  after  a  copy  of  Mr.  Newton's 
letter  of  the  10th  of  December,  1672,  had  been  sent 
to  Paris  to  be  communicated  to  him  ;  and  above  foui 
years  after,  Mr.  Collins  began  to  communicate  that 
fetter  to  his  correspondent;  in  which  letter  the 
method  of  fluxions  was  sufficiently  described  to  any 
intelligent  person. 

"  III.  That  by  Mr.  Newton's  letter  of  the  13th  of 
June,  1676,  it  appears  that  he  had  the  method  of 
fluxions  above  five  years  before  the  writing  of  that 
letter.  And  by  his  Analysis  per  ^Equationes  numero 
Terminorum  Infinitas,  communicated  by  Dr.  Barrow 
to  Mr.  Collins  in  July,  1669,  we  find  that  he  had  in- 
vented the  method  before  that  time. 

"  IV.  That  the  differential  method  is  one  and  the 
same  with  the  method  of  fluxions,  excepting  the 
name  and  mode  of  notation ;  Mr.  Leibnitz  calling 
those  quantities  differences  which  Mr.  Newton  calls 
moments  or  fluxions  ;  and  marking  them  with  the 
letter  d — a  mark  not  used  by  Mr.  Newton. 

"  And  therefore  we  take  the  proper  question  to  be 


192  SIR   ISAAC   NEWTON. 

not  who  invented  this  or  that  method,  but  who  was 
the  first  inventor  of  the  method.  And  we  believe 
that  those  who  have  reputed  Mr.  Leibnitz  the  first 
anventor  knew  little  or  nothing  of  his  correspondence 
with  Mr.  Collins  and  Mr.  Oldenburg  long  before,  noi 
of  Mr.  Newton's  having  that  method  above  fifteer 
Vears  before  Mr.  Leibnitz  began  to  publish  it  in  the 
Acta  Eruditorum  of  Leipsic. 

"  For  which  reason  we  reckon  Mr.  Newton  the 
first  inventor ;  and  are  of  opinion  that  Mr.  Keill,  in 
asserting  the  same,  has  been  no  ways  injurious  to 
Mr.  Leibnitz.  And  we  submit  to  the  judgment  of 
the  society  whether  the  extract  and  papers  now  pre- 
sented to  you,  together  with  what  is  extant  to  the 
same  purpose  in  Dr.  Wallis's  third  volume,  may  not 
deserve  to  be  made  public." 

This  report  being  read,  the  society  unanimously 
ordered  the  collection  of  letters  and  manuscripts  to 
be  printed,  and  appointed  Dr.  Halley,  Mr.  Jones,  and 
Mr.  Machin  to  superintend  the  press.  Complete 
copies  of  it,  under  the  title  of  Commercium  Epistoli- 
cwn  D.  Johannis  Collins  et  aliorum  de  analyst  promota, 
were  laid  before  the  society  on  the  8th  January,  1713, 
and  Sir  Isaac  Newton,  as  president,  ordered  a  copy 
to  be  delivered  to  each  person  of  the  committee  ap- 
pointed for  that  purpose,  to  examine  it  before  its 
publication. 

Leibnitz  received  information  of  the  appearance 
of  the  Commercium  Epistolicum  when  he  was  at 
Vienna;  and  "being  satisfied,"  as  he  expresses  it, 
"  that  it  must  contain  malicious  falsehoods,  I  did  not 
think  proper  to  send  for  it  by  post,  but  wrote  to  M. 
Bernouilli  to  give  me  his  sentiments.  M.  Bernoulli! 
wrote  me  a  letter  dated  at  Basle,  June  7th,  1713,  in 
which  he  said  that  it  appeared  probable  that  Sir  Isaac 
Newton  had  formed  his  calculus  after  having  seen 
mine"*  This  letter  was  published  by  a  friend  of 


*  Letter  to  Count  Bothman  in  Des  Maizeaux's  Recueil  de  diverse* 
vieces,  torn  ii,  p.  41, 45. 


COMMERCIUM   EPISTOLICUM.  193 

Leibnitz,  with  reflections,  in  a  loose  sheet  entitled 
Charta  Volans,  and  dated  July  29,  1713.  It  was 
widely  circulated  without  either  the  name  of  the 
author,  printer,  or  place  of  publication,  and  was 
communicated  to  the  Journal  Literaire  by  another 
friend  of  Leibnitz,  who  added  remarks  of  his  own, 
and  stated,  that  when  Newton  published  the  Principia 
in  1687,  he  did  not  understand  the  true  differential 
method ;  and  that  he  took  his  fluxions  from  Leibnitz. 

In  this  state  of  the  controversy,  Mr.  Chamberlayne 
conceived  the  design  of  reconciling  the  two  distin- 
guished philosophers ;  and  in  a  letter  dated  April  28, 
1714,*  he  addressed  himself  to  Leibnitz,  who  was 
still  at  Vienna.  In  replying  to  this  letter,  Leibnitz 
declared  that  he  had  given  no  occasion  for  the  dis- 
pute ;  "  that  Newton  procured  a  book  to  be  published, 
which  was  written  purposely  to  discredit  him,  and 
sent  it  to  Germany,  &c.  as  in  the  name  of  the 
society ;"  and  he  stated  that  there  was  room  to  doubt 
whether  Newton  knew  his  invention  before  he  had  it  of 
him.  Mr.  Chamberlayne  communicated  this  letter 
to  Sir  Isaac  Newton,  who  replied  that  Leibnitz  had 
attacked  his  reputation  in  1705,  by  intimating  that  he 
had  borrowed  from  him  the  method  of  fluxions ; 
that  if  Mr.  C.  could  point  out  to  him  any  thing  in 
which  he  had  injured  Mr.  Leibnitz,  he  would  give 
him  satisfaction ;  that  he  would  not  retract  things 
which  he  knew  to  be  true ;  and  that  he  believed  that 
the  Royal  Society  had  done  no  injustice  by  the  publi- 
cation of  the  Commercium  Epistolicum. 

The  Royal  Society,  having  learned  that  Leibnitz 
complained  of  their  having  condemned  him  unheard, 
inserted  a  declaration  in  their  journals  on  the  20th 
May,  1714,  that  they  did  not  pretend  that  the  report 
of  their  committee  should  pass  for  a  decision  of  the 
society.  Mr.  Chamberlayne  sent  a  copy  of  this  to 
Leibnitz,  along  with  Sir  Isaac's  letter,  and  Dr.  KeilTs 

*  See  Des  Maizeaux,  torn.  ii.  p.  116. 
R 


194  SIR   ISAAC   NEWTON. 

answer  to  'the  papers  inserted  in  the  Journal  Lite- 
raire.  After  perusing  these  documents,  M.  Leibnitz 
replied,  "  that  Sir  Isaac's  letter  was  written  with 
very  little  civility;  that  he  was  not  in  a  humour 
to  put  himself  in  a  passion  against  such  people; 
that  there  were  other  letters  among  those  of  Olden- 
burg and  Collins  which  should  have  been  published; 
and  that  on  his  return  to  Hanover,  he  would  be  able 
to  publish  a  Commercium  Epistolicum  which  would 
be  of  service  to  the  history  of  learning."  When 
this  letter  was  read  to  the  Royal  Society,  Sir  Isaac 
remarked,  that  the  last  part  of  it  injuriously  accused 
the  society  of  having  made  a  partial  selection  of 
papers  for  the  Commercium  Epistolicum ;  that  he 
did  not  interfere  in  any  way  in  the  publication  of 
that  work,  and  had  even  withheld  from  the  com- 
mittee two  letters,  one  from  Leibnitz  in  1693,  and 
another  from  Wallis  in  1695,  which  were  highly 
favourable  to  his  cause.  He  stated  that  he  did  not 
think  it  right  for  M.  Leibnitz  himself,  but  that,  if 
he  had  letters  to  produce  in  his  favour,  that  they 
might  be  published  in  the  Philosophical  Transac- 
tions, or  in  Germany. 

About  this  time  the  Abbe  Conti,  a  noble  Vene- 
tian, came  to  England.  He  was  a  correspondent  of 
Leibnitz,  and  in  a  letter  which  he  had  received  soon 
after  his  arrival,*  he  enters  upon  his  dispute  with 
Newton.  He  charges  the  English  "with  wishing 
,  to  pass  for  almost  the  only  inventors."  He  declares 
"  that  Bernouilli  had  judged  rightly  in  saying  that 
Newton  did  not  possess  before  him  the  infinitesimal 
characteristic  and  algorithm."  He  remarks  that 
Newton  preceded  him  only  in  series;  and  he  con- 
fesses that  during  his  second  visit  to  England,  "Col- 
lins showed  him  part  of  his  correspondence,"  or,  as 
he  afterward  expresses  it,  he  saw  "  some  of  the  let- 
ters of  Newton  at  Mr.  Collins's."  He  then  attacks 

*  Written  in  November  or  December,  1715. 


COMMERCIUM   EPISTOLICUM.  195 

Sir  Isaac's  philosophy,  particularly  his  opinions 
about  gravity  and  vacuum,  the  intervention  of  God 
for  the  preservation  of  his  creatures  ;  and  he  accuses 
him  of  reviving  the  occult  qualities  of  the  schools. 
But  the  most  remarkable  passage  in  this  letter  is 
the  following :  "  I  am  a  great  friend  of  experimental 
philosophy,  but  Newton  deviates  much  from  it  when 
he  pretends  that  all  matter  is  heavy,  or  that  each  par- 
ticle of  matter  attracts  every  other  particle." 

The  above  letter  to  the  Abbe  Conti  was  generally 
shown  in  London,  and  came  to  be  much  talked  of  at 
court,  in  consequence  of  Leibnitz  having  been  privy 
counsellor  to  the  Elector  of  Hanover  when  that 
prince  ascended  the  throne  of  England.  Many 
persons  of  distinction,  and  particularly  the  Abbe 
Conti,  urged  Newton  to  reply  to  Leibnitz's  letter, 
but  he  resisted  all  their  solicitations.  One  day, 
however,  King  George  I.  inquired  when  Sir  Isaac 
Newton's  answer  to  Leibnitz  would  appear;  and 
when  Sir  Isaac  heard  this,  he  addressed  a  long  reply 
to  the  Abbe  Conti,  dated  February  26th,  0.  S.  1715- 
16.  This  letter,  written  with  dignified  severity,  is 
a  triumphant  refutation  of  the  allegations  of  his  ad- 
versary ;  and  the  following  passage  deserves  to  be 
quoted,  as  connected  with  that  branch  of  the  dispute 
which  relates  to  Leibnitz's  having  seen  part  of 
Newton's  letters  to  Mr.  Collins.  "  He  complains 
of  the  committee  of  the  Royal  Society,  as  if  they 
had  acted  partially  in  omitting  what  made*  against 
me ;  but  he  fails  in  proving  the  accusation.  For  he 
instances  in  a  paragraph  concerning  my  ignorance, 
pretending  that  they  omitted  it,  and  yet  you  will 
rind  it  in  the  Commercium  Epistolicum,  p.  547,  lines 
2,  3,  and  I  am  not  ashamed  of  it.  He  saith  that  he 
saw  this  paragraph  in  the  hands  of  Mr.  Collins  when 
he  was  in  London  the  second  time,  that  is  in  Octo- 
ber, 1676.  It  is  in  my  letter  of  the  24th  of  October, 
1676,  and  therefore  he  then  saw  that  letter.  And 


196  SIR  ISAAC   NEWTON. 

in  that  and  some  other  letters  writ  before  that  time,' 
I  described  rny  method  of  fluxions ;  and  in  the  same 
letter  I  described  also  two  general  methods  of  series, 
one  of  which  is  now  claimed  from  me  by  Mr.  Leib- 
nitz." The  letter  concludes  with  the  following 
paragraph :  "  But  as  he  has  lately  attacked  me  with 
an  accusation  which  amounts  to  plagiary ;  if  he  goes 
on  to  accuse  me,  it  lies  upon  him  by  the  laws  of  all 
nations  to  prove  his  accusations,  on  pain  of  being 
accounted  guilty  of  calumny.  He  hath  hitherto 
written  letters  to  his  correspondents  full  of  affirma- 
tions, complaints,  and  reflections,  without  proving 
any  thing.  But  he  is  the  aggressor,  and  it  lies  upon 
him  to  prove  the  charge." 

In  transmitting  this  letter  to  Leibnitz,  the  Abbe 
Conti  informed  him  that  he  himself  had  read  with 
great  attention,  and  without  the  least  prejudice,  the 
Commercium  Epistolicum,  and  the  little  piece*  that 
contains  the  extract ;  that  he  had  also  seen  at  the 
Royal  Society  the  original  papers  of  the  Commer- 
cium Epistolicum,  and  some  other  original  pieces 
relating  to  it.  "  From  all  this,"  says  he,  "I  infer, 
that,  if  all  the  digressions  are  cut  off,  the  only  point 
is,  whether  Sir  Isaac  Newton  had  the  method  of 
fluxions  or  infinitesimals  before  you,  or  whether  you 
had  it  before  him.  You  published  it  first,  it  is  true, 
but  you  have  owned  also  that  Sir  Isaac  Newton  had 
given  many  hints  of  it  in  his  letters  to  Mr.  Olden- 
burg and  others.  This  is  proved  very  largely  in  the 
Commercium,  and  in  the  extract  of  it.  What  an- 
swer do  you  give  ?  This  is  still  wanting  to  the 
public,  in  order  to  form  an  exact  judgment  of  the 
affair."  The  Abbe  adds,  that  Mr.  Leibnitz's  own 
friends  waited  for  his  answer  with  great  impatience, 
and  that  they  thought  he  could  not  dispense  with 
answering,  if  not  Dr.  Keill,  at  least  Sir  Isaac  New- 

*  This  is  the  Recensio  Commercii  Ipistolici,  or  review  of  it,  which 
was  first  published  in  the  Phil.  Trans*  1715. 


GENERAL  VIEW  OF  THE  CONTROVERSY.   197 

ton  himself,  who  had  given  him  a  defiance  in  express 
terms. 

Leibnitz  was  not  long-  in  complying  with  this 
request.  He  addressed  a  letter  to  the  Abbe  Conti, 
dated  April  9th,  1716,  but  he  sent  it  through  M.  Ra- 
mond  at  Paris,  to  communicate  it  to  others.  When 
it  was  received  by  the  Abbe  Conti,  Newton  wrote 
observations  upon  it,  which  were  communicated 
only  to  some  of  his  friends,  and  which,  while  they 
placed  his  defence  on  the  most  impregnable  basis, 
at  the  same  time  threw  much  light  on  the  early  his- 
tory of  his  mathematical  discoveries. 

The  death  of  Leibnitz  on  the  14th  November, 
1716,  put  an  end  to  this  controversy,  and  Newton 
some  time  afterward  published  the  correspondence 
with  the  Abbe  Conti,  which  had  hitherto  been  only 
privately  circulated  among  the  friends  of  the  dispu- 
tants.* 

In  1722,  a  new  edition  of  the  Commercium  Epis- 
tolicum  was  published,  and  there  was  prefixed  to  it 
a  general  review  of  its  contents,  which  has  been 
falsely  ascribed  to  Newton. f  When  the  third  edi- 

*  M.  Biot  remarks,  that  the  animosity  of  Newton  was  not  calmed  by 
the  death  of  Leibnitz,  for  he  had  no  sooner  heard  of  it  than  he  caused  to 
be  printed  two  manuscript  letters  of  Leibnitz,  written  in  the  preceding 
year,  accompanying  them  with  a  very  bitter  refutation  (en  les  accom- 
pagnant  d'un  refutation  tres-amere).  Who  that  reads  this  sentence 
does  not  believe  that  the  bitter  refutation  was  written  after  Leibnitz's 
death  ?  The  animosity  could  not  be  shown  by  the  simple  publication 
of  the  letters.  It  could  reside  only  in  the  bitterness  of  the  refutation. 
The  implied  charge  is  untrue  ;  the  bitter  refutation  was  written  before 
Leibnitz's  death,  and  consequently  he  showed  no  animosity  over  the 
grave  of  his  rival ;  and  in  our  opinion  none  even  before  his  death. 

1  M.  Biot  states  that  Sir  Isaac  Newton  caused  this  edition  of  the 
Commercium  Epistolicum  to  be  printed ;  that  Sir  Isaac  placed  at  the 
head  of  it  a  partial  abstract  of  the  collection  ;  and  that  this  abstract 
appeared  to  have  been  written  by  himself  These  groundless  charges 
may  be  placed,  without  any  refutation,  beside  the  assertion  of  Montucla, 
that  Newton  wrote  the  notes  (les  notes)  on  the  Commercium  Epis- 
tolicum ;  and  the  equally  incorrect  statement  of  La  Croix,  that 
Newton  added  to  it  notes  (des  notes),  with  his  own  hand.  We  should 
not  h-rve  noticed  the  charges  of  M.  Bior,  had  he  not  adduced  them  as 
proofs  of  Newton's  animosity  to  Leibnitz  after  his  death.  See  Mr. 
Herschel's  H  istory  of  Mathematics  in  the  Edinburgh  Encyclopedia^ 
ToL  xiii.  p.  368,  note. 

R2 


198  SIR   ISAAC   NEWTON. 

tion  of  the  Principia  was  published  in  1725,  the 
celebrated  scholium  which  we  have  already  quoted, 
and  in  which  Leibnitz's  differential  calculus  was 
mentioned,  was  struck  out  either  by  Newton  or  by 
the  editor.  This  step  was  perhaps  rash  and  ill- 
advised  ;  but  as  the  scholium  had  been  adduced  by 
Leibnitz  and  others  as  a  proof  that  Newton  acknow- 
ledged him  to  be  an  independent  inventor  of  the 
calculus, — an  interpretation  which  it  does  not  bear, 
and  which  Newton  expressly  states  he  never  in- 
tended it  to  bear, — he  was  justified  in  withdrawing 
a  passage  which  had  been  so  erroneously  inter- 
preted, and  so  greatly  misapplied. 

In  viewing  this  controversy,  at  the  distance  of 
more  than  a  century,  when  the  passions  of  the  in- 
dividual combatants  have  been  allayed,  and  national 
jealousies  extinguished,  it  is  not  difficult  to  form  a 
correct  estimate  of  the  conduct  and  claims  of  the 
two  rival  analysts.  By  the  unanimous  verdict  of 
all  nations,  it  has  been  decided  that  Newton  invented 
fluxions  at  least  ten  years  before  Leibnitz.  Some 
of  the  letters  of  Newton  which  bore  reference  to 
this  great  discovery  were  perused  by  the  German 
mathematician ;  but  there  is  no  evidence  whatever 
that  he  borrowed  his  differential  calculus  from  these 
letters.  Newton  was  therefore  the  first  inventor, 
and  Leibnitz  the  second.  It  was  impossible  that  the 
former  could  have  been  a  plagiarist;  but  it  was 
possible  for  the  latter.  Had  the  letters  of  Newton 
contained  even  stronger  indications  than  they  do  of 
the  new  calculus,  no  evidence  short  of  proof  could 
have  justified  any  allegation  against  Leibnitz's 
honour.  The  talents  which  he  displayed  in  the  im- 
provement of  the  calculus  showed  that  he  was 
capable  of  inventing  it;  and  his  character  stood 
sufficiently  high  to  repel  every  suspicion  of  his  in- 
tegrity. But  if  it  would  have  been  criminal  to 
charge  Leibnitz  with  plagiarism,  what  must  we 
think  of  those  who  dared  to  accuse  Newton  of  bor 


GENERAL  VIEW  OF  THE  CONTROVERSY.   199 

I 

rowing  his  fluxions  from  Leibnitz?  This  odious 
accusation  was  made  by  Leibnitz  himself,  and  by 
Bernouilli ;  and  we  have  seen  that  the  former  re- 
peated it  again  and  again,  as  if  his  own  good  name 
rested  on  the  destruction  of  that  of  his  rival.  It  was 
this  charge  against  Newton  that  gave  rise  to  the  at- 
tack of  Keill,  and  the  publication  of  the  Commercium 
Epistolicum ;  and,  notwithstanding  this  high  provo- 
cation, the  committee  of  the  Royal  Society  contented 
themselves  with  asserting  Newton's  priority,  with- 
out retorting  the  charge  of  plagiarism  upon  his  rival. 

Although  an  attempt  has  been  recently  made  to 
place  the  conduct  of  Leibnitz  on  the  same  level  with 
that  of  Newton,  yet  the  circumstances  of  the  case 
will  by  no  means  justify  such  a  comparison.  The 
conduct  of  Newton  was  at  all  times  dignified  and 
just.  He  knew  his  rights,  and  he  boldly  claimed 
them.  Conscious  of  his  integrity,  he  spurned  with 
indignation  the  charge  of  plagiarism  with  which  an 
ungenerous  rival  had  so  insidiously  loaded  him ;  and 
if  there  was  one  step  in  his  frank  and  unhesitating 
procedure  which  posterity  can  blame  it  is  his  omis- 
sion, in  the  third  edition  of  the  Principia,  of  the 
references  to  the  differential  calculus  of  Leibnitz. 
This  omission,  however,  was  perfectly^  just.  The 
scholium  which  he  had  left  out  was  a  mere  historical 
statement  of  the  fact,  that  the  German  mathemati- 
cian had  sent  him  a  method  which  was  the  same  as 
his  own ;  and  when  he  found  that  this  simple  asser- 
tion had  been  held  by  Leibnitz  and  others  as  a  re- 
cognition of  his  independent  claim  to  the  invention, 
he  was  bound  either  to  omit  it  altogether,  or  to 
enter  into  explanations  which  might  have  involved 
him  in  a  new  controversy. 

The  conduct  of  Leibnitz  was  not  marked  with  the 
same  noble  lineaments.  That  he  was  the  aggressor 
is  universally  allowed.  That  he  first  dared  to 
breathe  the  charge  of  plagiarism  against  Newton, 
and  that  he  often  referred  to  it,  has  been  sufficiently 


200  SIR   ISAAC   NEWTON. 

apparent;  and  when  arguments  failed  him  he  had 
recourse  to  threats — declaring  that  he  would  publish 
another  Commercium  Epistolicum,  though  he  had 
no  appropriate  letters  to  produce.  All  this  is  now 
matter  of  hietory ;  and  we  may  find  some  apology 
for  it  in  his  excited  feelings,  and  in  the  insinuations 
which  were  occasionally  thrown  out  against  the 
originality  of  his  discovery.;  but  for  other  parts  of 
his  conduct  we  seek  in  vain  for  an  excuse.  When 
he  assailed  the  philosophy  of  Newton  in  his  letters 
to  the  Abbe  Conti,  he  exhibited  perhaps  only  the 
petty  feelings  of  a  rival ;  but  when  he  dared  to  ca- 
lumniate that  great  man  in  his  correspondence  with 
the  Princess  of  Wales,  by  whom  he  was  respected 
and  beloved;  when  he  ventured  to  represent  the 
Newtonian  philosophy  as  physically  false,  and  as 
dangerous  to  religion ;  and  when  he  founded  these 
accusations  on  passages  in  the  Principia  and  the 
Optics  glowing  with  all  the  fervour  of  genuine 
piety,  he  cast  a  blot  upon  his  name,  which  all  his 
talents  as  a  philosopher,  and  all  his  virtues  as  a  man, 
will  never  be  able  to  efface. 


CHAPTER  XIII. 

James  IT.  attacks  the  Privileges  of  the  University  of  Cambridge — New- 
Ion  chosen  one  of  the  Delegates  to  resist  this  Encroachment — He  is 
elected  a  Member  of  the  Convention  Parliament — Burning  of  his 
Manuscripts— His  supposed  Derangement  of  Mind — View  taken  of 
this  by  foreign  Philosophers — His  Correspondence  with  Mr.  Ptpys 
and  Mr  1  Locke  at  the  time  of  his  Illness— Mr.  Millingtori's  Letter  to 
Mr.  Pepys  on  the  subject  of  Newton's  Illness — Refutation  of  the 
Statement  that  he  laboured  under  Mental  Derangement. 

FROM  the  year  1669,  when  Newton  was  installed 
in  the  Lucasian  chair,  till  1095,  when  he  ceased  to 
reside  in  Cambridge,  he  seems  to  have  been  seldom 
absent  from  his  college  more  than  three  or  four 


UNIVERSITY   OF   CAMBRIDGE.  201 

ireeks  in  the  year.  In  1675,  he  received  a  dispensa- 
tion from  Charles  II.  to  continue  in  his  fellowship 
of  Trinity  College  without  taking  orders,  and  we 
have  already  seen  in  the  preceding  chapter  how  his 
time  was  occupied  till  the  publication  of  the  Principia 
in  1687. 

An  event  now  occurred  which  drew  Newton  from 
the  seclusion  of  his  studies,  and  placed  him  upon  the 
theatre  of  public  life.  Desirous  of  re-establishing 
the  Catholic  faith  in  its  former  supremacy,  King 
James  II.  had  begun  to  assail  the  rights  and  privi- 
leges of  his  Protestant  subjects.  Among  other  illegal 
acts,  he  sent  his  letter  of  mandamus  to  the  University 
of  Cambridge  to  order  Father  Francis,  an  ignorant 
monk  of  the  Benedictine  order,  to  be  received  as 
master  of  arts,  and  to  enjoy  all  the  privileges  of  this 
degree,  without  taking  the  oaths  of  allegiance  and 
supremacy.  The  university  speedily  perceived  the 
consequences  which  might  arise  from  such  a  meas- 
ure. Independent  of  the  infringement  of  their  rights 
which  such  an  order  involved,  it  was  obvious  that 
the  highest  interests  of  the  university  were  endan- 
gered, and  that  Roman  Catholics  might  soon  become 
a  majority  in  the  convocation.  They  therefore 
unanimously  refused  to  listen  to  the  royal  order,  and 
they  did  this  with  a  firmness  of  purpose  which  irri- 
tated the  despotic  court.  The  king  reiterated  his 
commands,  and  accompanied  them  with  the  severest 
threatenings  in  case  of  disobedience.  The  Catho- 
lics were  not  idle  in  supporting  the  views  of  the 
sovereign.  The  honorary  degree  of  M.A.  which 
conveys  no  civil  rights  to  its  possessor,  having  been 
formerly  given  to  the  secretary  of  the  ambassador 
from  Morocco,  it  was  triumphantly  urged  that  the 
University  of  Cambridge  had  a  greater  regard  for  a 
Mahometan  than  for  a  Roman  Catholic,  and  was 
more  obsequious  to  the  ambassador  from  Morocco 
than  to  their  own  lawful  sovereign.  Though  this 
reasoning  might  impose  upon  the  ignorant,  it  pro- 


202  SIR   ISAAC   NEWTON. 

duced  little  effect  upon  the  members  of  the  univer- 
sity. A  few  weak-minded  individuals,  however, 
were  disposed  to  yield  a  reluctant  consent  to  the 
royal  wishes.  They  proposed  to  confer  the  degree, 
and  at  the  same  time  to  resolve  that  it  should  not  in 
future  be  regarded  as  a  precedent.  To  this  it  was 
replied,  that  the  very  act  of  submission  in  one  case 
would  be  a  stronger  argument  for  continuing  the 
practice  than  any  such  resolution  would  be  against 
its  repetition.  The  university  accordingly  remained 
firm  in  their  original  decision.  The  vice-chancellor 
was  summoned  before  the  ecclesiastical  commission 
to  answer  for  this  act  of  contempt.  Newton  was 
among  the  number  of  those  who  resisted  the  wishes 
of  the  court,  and  he  was  consequently  chosen  one 
of  the  nine  delegates  who  were  appointed  to  defend 
the  independence  of  the  university.  These  dele- 
gates appeared  before  the  High  Court.  They  main- 
tained that  not  a  single  precedent  could  be  found  to 
justify  so  extraordinary  a  measure ;  and  they  showed 
that  Charles  II.  had,  under  similar  circumstances, 
been  pleased  to  withdraw  his  mandamus.  This 
representation  had  its  full  weight,  and  the  king  was 
induced  to  abandon  his  design.* 

The  part  which  Newton  had  taken  in  this  affair, 
and  the  high  character  which  he  now  held  in  the 
scientific  world,  induced  his  friends  to  propose  him 
as  member  of  parliament  for  the  university.  He 
was  accordingly  elected  in  1688,  though  by  a  very 
narrow  majority,!  and  he  sat  in  the  Convention 
Parliament  till  its  dissolution.  In  the  year  1688 
and  1689,  Newton  was  absent  from  Cambridge  during 
the  greater  part  of  the  year,  owing,  we  presume,  to 
his  attendance  in  parliament;  but  it  appears  from 

*  See  Burnet's  History  of  his  own  Times,  vol.  i.  p.  697.  Lond.  1724. 
1  The  other  candidates  were  Sir  Robert  Sawyer  and  Mr.  Finch,  ami 
the  votes  stood  thus. 

Sir  Robert  Sawyer,    125 

Mr.  Newton,  122 

Mr.  Finch,  117 


BURNING   OF   HIS    MANUSCRIPTS.  203 

lie  books  of  the  University  that  from  1690  to  1695 
le  was  seldom  absent,  and  must  therefore  have 
renounced  his  parliamentary  duties. 

During  his  stay  in  London  he  had  no  doubt  expe- 
rienced the  unsuitableness  of  his  income  to  the  new 
rircum stances  in  which  he  was  placed,  and  it  is 
probable  that  this  was  the  cause  of  the  limitation 
)f  his  residence  to  Cambridge.  His  income  was 
certainly  very  confined,  and  but  little  suited  to  the 
generosity  of  his  disposition.  Demands  were  doubt- 
ess  made  upon  it  by  some  of  his  less  wealthy  rela- 
ives  ;  and  there  is  reason  to  think  that  he  himself, 
is  well  as  his  influential  friends,  had  been  looking 
"orward  to  some  act  of  liberality  on  the  part  of  the 
;overnment. 

An  event  however  occurred  which  will  ever  form 
an  epoch  in  his  history ;  and  it  is  a  singular  circum- 
stance, that  this  incident  has  been  for  more  than  a 
century  unknown  to  his  own  countrymen,  and  has 
>een  accidentally  brought  to  light  by  the  examina- 
ion  of  the  manuscripts  of  Huygens.  This  event 
has  been  magnified  into  a  temporary  aberration  of 
nind,  which  is  said  to  have  arisen  from  a  cause 
scarcely  adequate  to  its  production. 

While  he  was  attending  divine  service  in  a  winter 
norning,  he  had  left  in  his  study  a  favourite  little 
dog  called  Diamond.  Upon  returning  from  chapel 
found  that  it  had  overturned  a  lighted  taper  on 
lis  desk,  which  set  fire  to  several  papers  on  which 
he  had  recorded  the  results  of  some  optical  experi- 
ments. These  papers  are  said  to  have  contained  the 
Labours  of  many  years,  and  it  has  been  stated  that 
when  Mr.  Newton  perceived  the  magnitude  of  his  loss, 
be  exclaimed,  "  Oh,  Diamond,  Diamond,  little  do  you 
know  the  mischief  you  have  done  me !"  It  is  a 
curious  circumstance  that  Newton  never  refers  to 
the  experiments  which  he  is  said  to  have  lost  on  this 
occasion,  and  his  nephew,  Mr.  Conduit,  makes  no 
allusion  to  the  event  itself.  The  distress,  however 


204  SIR   ISAAC  NEWTON. 

which  it  occasioned  is  said  to  have  been  so  deep  a» 
to  affect  even  the  powers  of  his  understanding. 

This  extraordinary  effect  was  first  communicated 
to  the  world  in  the  Life  of  Newton  by  M.  Biot,  who 
received  the  following  account  of  it  from  the  cele- 
brated M.  Van  Swinden. 

"There  is  among  the  manuscripts  of  the  cele- 
brated Huygens  a  small  journal  in  folio,  in  which 
he  used  to  note  down  different  occurrences.  It  is 
side  £  No.  8,  p.  112,  in  the  catalogue  of  the  library 
of  Leyden.  The  following  extract  is  written  by 
Huygens  himself,  with  whose  handwriting  I  am  well 
acquainted,  having  had  occasion  to  peruse  several 
of  his  manuscripts  and  autograph  letters.  '  On  the 
29th  May,  1694,  M.  Colin,*  a  Scotsman,  informed  me 
that  eighteen  months  ago  the  illustrious  geometer,  Isaac 
Newton,  had  become  insane,  either  in  consequence  of 
his  too  intense  application  to  his  studies,  or  from  ex- 
cessive grief  at  having  lost,  by  fire,  his  chymical  labora- 
tory and  several  manuscripts.  When  he  came  to  the 
Archbishop  of  Cambridge,  he  made  some  observations 
which  indicated  an  alienation  of  mind.  He  was  imme- 
diately taken  care  of  by  his  friends,  who  confined  him  to 
his  house  and  applied  remedies,  by  means  of  which  he 
had  now  so  far  recovered  his  health  that  he  began  to  under- 
stand the  PrincipiaS  "  Huygens  mentioned  this  cir- 
cumstance to  Leibnitz,  in  a  letter  dated  8th  June. 
1694,  to  which  Leibnitz  replies  in  a  letter  dated  the 
23d,  "  I  am  very  glad  that  I  received  information  of 
1  the  cure  of  Mr.  Newton,  at  the  same  time  that  I  firsl 
heard  of  his  illness,  which  doubtless  must  have  beer 

*  This  M.  Colin  was  probably  a  young  bachelor  of  arts  whom  New 
ton  seems  afterward  to  have  employed  in  some  of  his  calculations 
These  bachelors  were  distinguished  by  the  title  of  Dominus,  and  it  was 
usual  to  translate  this  word  and  to  call  them  Sir.  In  a  letter  from  New 
ton  to  Flamstead,  dated  Cambridge,  June  29th,  1695,  is  the  following 
passage :  "  I  want  not  your  calculations,  but  your  observations  only,  for 
besides  myself  and  my  servant,  Sir  Collins  (whom  I  can  employ  for  f 
little  money,  which  I  value  not)  tells  me  that  he  can  calculate  "an  eclipw 
and  work  truly. 


STATE    OF   HIS   MIND.  205 

very  alarming.  '  It  is  to  men  like  you  and  him,  sir, 
that  I  wish  a  long  life.'  " 

The  first  publication  of  the  preceding  statement 
produced  a  strong  sensation  among  the  friends  and 
admirers  of  Newton.  They  could  not  easily  believe 
in  the  prostration  of  that  intellectual  strength  which 
had  unbarred  the  strongholds  of  the  universe.  The 
unbroken  equanimity  of  Newton's  mind,  the  purity 
of  his  moral  character,  his  temperate  and  abstemious 
life,  his  ardent  and  unaffected  piety,  and  the  weak- 
ness of  his  imaginative  powers,  all  indicated  a  mind 
which  was  not  likely  to  be  overset  by  any  affliction 
to  which  it  could  be  exposed.  The  loss  of  a  few 
ixperimental  records  could  never  have  disturbed  the 
equilibrium  of  a  mind  like  his.  If  they  were  the 
records  of  discoveries,  the  discoveries  themselves 
ndestructible  would  have  been  afterward  given  to 
the  world.  If  they  were  merely  the  details  of  ex- 
Derimental  results,  a  little  time  could  have  easily 
'eproduced  them.  Had  these  records  contained  the 
irst  fruits  of  early  genius — of  obscure  talent,  on 
which  fame  had  not  yet  shed  its  rays,  we  might  have 
supposed  that  the  first  blight  of  such  early  ambition 
would  have  unsettled  the  stability  of  an  untried 
mind.  But  Newton  was  satiated  with  fame.  His 
mightiest  discoveries  were  completed  and  diffused 
over  all  Europe,  and  he  must  have  felt  himself 
)laced  on  the  loftiest  pinnacle  of  earthly  ambition. 
The  incredulity  which  such  views  could  not  fail  to 
encourage  was  increased  by  the  novelty  of  the  in. 
rormation.  No  English  biographer  had  ever  alluded 
o  such  an  event.  History  and  tradition  were  equally 
silent,  and  it  was  not  easy  to  believe  that  the  Luca- 
sian  Professor  of  Mathematics  at  Cambridge,  a  mem- 
ber of  the  English  parliament,  and  the  first  philoso- 
pher in  Europe  could  have  lost  his  reason  without 
the  dreadful  fact  being  known  to  his  own  countrymen. 

But  if  the  friends  of  Newton  were  surprised  by 
the  nature  of  the  intelligence,  they  wrere  distressed 
S 


206  SIR   ISAAC   NEWTON* 

at  the  view  which  was  taken  of  it  by  foreign  philoso- 
phers. While  one  maintained  that  the  intellectual 
exertions  of  Newton  had  terminated  with  the  publica- 
tion of  the  Principia,  and  that  the  derangement  of 
his  mind  was  the  cause  of  his  abandoning  the  sci- 
ences, others  indirectly  questioned  the  sincerity  of 
his  religious  views,  and  ascribed  to  the  aberration 
of  his  mind  those  theological  pursuits  which  gilded 
his  declining  age.  "  But  the  fact,"  says  M.  Biot, 
"  of  the  derangement  of  his  intellect,  whatever  may 
have  been  the  cause  of  it,  will  explain  why,  after  the 
publication  of  the  Principia  in  1687,  Newton,  though 
only  forty-five  years  old,  never  more  published  a 
new  work  on  any  branch  of  science,  but  contented 
himself  with  giving  to  the  world  those  which  he  had 
composed  long  before  that  epoch,  confining  himself 
to  the  completion  of  those  parts  which  might  require 
development.  We  may  also  remark,  that  even 
these  developments  appear  always  to  be  derived 
from  experiments  and  observations  formerly  made, 
such  as  the  additions  to  the  second  edition  of  the 
Principia,  published  in  1713,  the  experiments  on 
thick  plates,  those  on  diffraction,  and  the  chymical 
queries  placed  at  the  end  of  the  Optics  in  1704 ;  for 
in  giving  an  account  of  these  experiments  Newton 
distinctly  says  that  they  were  taken  from  ancient 
manuscripts  which  he  had  formerly  composed ;  and 
he  adds,  that  though  he  felt  the  necessity  of  extend- 
ing them,  or  rendering  them  more  perfect,  he  was 
not  able  to  resolve  to  do  this,  these  matters  being  no 
longer  in  his  way.  Thus  it  appears  that  though  he 
had  recovered  his  health  sufficiently  to  understand 
all  his  researches,  and  even  in  some  cases  to  make 
additions  to  them,  and  useful  alterations,  as  appears 
from  the  second  edition  of  the  Principia,  for  which 
he  kept  up  a  very  active  mathematical  correspond- 
ence with  Mr.  Cotes,  yet  he  did  not  wish  to  under- 
take new  labours  in  those  departments  t>f  science 
where  he  had  done  so  much,  and  where  he  so  dis- 


STATE    OF   HIS    MIND.  207 

tinctly  saw  what  remained  to  be  done."  Under  the 
influence  of  the  same  opinion,  M.  Biot  finds  "  it  ex- 
tremely probable  that  his  dissertation  on  the  scale 
of  heat  was  written  before  the  fire  in  his  laboratory;" 
he  describes  Newton's  conduct  about  the  longitude 
bill  as  "  almost  puerile  on  so  solemn  an  occasion, 
and  one  which  might  lead  to  the  strangest  conclu- 
sions, particularly  if  we  refer  it  to  the  fatal  accident 
which  Newton  had  suffered  in  1695." 

The  celebrated  Marquis  de  la  Place  viewed  the 
illness  of  Newton  in  a  light  still  more  painful  to  his 
friends.  He  maintained  that  he  never  recovered  the 
vigour  of  his  intellect,  and  he  was  persuaded  that 
Newton's  theological  inquiries  did  not  commence 
till  after  that  afflicting  epoch  of  his  life.  He  even 
commissioned  Professor  Gautier  of  Geneva  to  make 
inquiries  on  this  subject  during  his  visit  to  England, 
as  if  it  concerned  the  interests  of  truth  and  justice 
to  show  that  Newton  became  a  Christian  and  a 
theological  writer  only  after  the  decay  of  his 
strength  and  the  eclipse  of  his  reason. 

Such  having  been  the  consequences  of  the  dis- 
closure of  Newton's  illness  by  the  manuscript  of 
Huygens,  I  felt  it  to  be  a  sacred  duty  to  the  memory 
of  that  great  man,  to  the  feelings  of  his  countrymen, 
and  to  the  interests  of  Christianity  itself,  to  inquire 
into  the  nature  and  history  of  that  indisposition 
which  seems  to  have  been  so  much  misrepresented 
and  misapplied.  From  the  ignorance  of  so  extraor- 
dinary an  event  which  has  prevailed  for  such  a  long 
period  in  England,  it  might  have  been  urged  with 
some  plausibility  that  Huygens  had  mistaken  the 
real  import  of  the  information  that  was  conveyed  to 
him ;  or  that  the  Scotchman  from  whom  he  received 
it  had  propagated  an  idle  and  a  groundless  rumour. 
But  we  are,  fortunately,  not  confined  to  this  very 
reasonable  mode  of  defence.  There  exists  at  Cam- 
bridge a  manuscript  journal  written  by  Mr.  Abraham 
de  la  Pryme,  who  was  a  student  in  the  university 


208  SIR   ISAAC   NEWTON. 

while  Newton  was  a  fellow  of  Trinity.  This  manu- 
script is  entitled  "  Ephemeris  Vita,  or  Diary  of  my 
own  Life,  containing  an  account  likewise  of  the  most 
observable  and  remarkable  things  that  I  have  taken 
notice  of  from  my  youth  up  hitherto."  Mr.  de  la 
Pryme  was  born  in  1671,  and  begins  the  diary  in 
1685.  This  manuscript  is  in  the  possession  of  his 
collateral  descendant,  George  Pryme,  Esq.,  Profes- 
sor of  Political  Economy  at  Cambridge,  to  whom  I 
have  been  indebted  for  the  following  extract. 

"  1692,  February  3d. — What  I  heard  to-day  I  must 
relate.  There  is  one  Mr.  Newton  (whom  I  have 
very  oft  seen),  Fellow  of  Trinity  College,  that  is 
mighty  famous  for  his  learning,  being  a  most  excel- 
lent mathematician,  philosopher,  divine,  &c.  He 
has  been  Fellow  of  the  Royal  Society  these  many 
years;  and  among  other  very  learned  books  and 
tracts,  he's  written  one  upon  the  mathematical  prin- 
ciples of  philosophy,  which  has  got  him  a  mighty 
name,  he  having  received,  especially  from  Scotland, 
abundance  of  congratulatory  letters  for  the  same ; 
but  of  all  the  books  that  he  ever  wrote,  there  was 
one  of  colours  and  light,  established  upon  thousands 
of  experiments  which  he  had  been  twenty  years  of 
making,  and  which  had  cost  him  many  hundred  of 
pounds.  This  book,  which  he  valued  so  much,  and 
which  was  so  much  talked  of,  had  the  ill  luck  to 
perish  and  be  utterly  lost  just  when  the  learned 
author  was  almost  at  putting  a  conclusion  at  the 
same,  after  this  manner:  In  a  winter's  morning, 
leaving  it  among  his  other  papers  on  his  study  table 
while  he  went  to  chapel,  the  candle,  which  he  had 
unfortunately  left  burning  there  too,  catched  hold 
by  some  means  of  other  papers,  and  they  fired  the 
aforesaid  book,  and  utterly  consumed  it  and  several 
other  valuable  writings ;  and,  which  is  most  wonder- 
ful, did  no  further  mischief.  But  when  Mr.  Newton 
came  from  chapel,  and  had  seen  what  was  done, 
every  one  thought  he  would  have  run  mad,  he  wa» 


STATE    OF   HIS   MIND.  209 

50  troubled  thereat  that  he  was  not  himself  for  a 
nonth  after.     A  long  account  of  this  his  system  of 
ight  and  colours  you  may  find  in  the  Transactions 
)f  the  Royal  Society,  which  he  had  sent  up  to  them 
ong  before  this  sad  mischance  happened  unto  him." 
From  this  extract  we  are  enabled  to  fix  the  ap- 
roximate  date  of  the  accident  by  which  Newton 
ost  his  papers.    It  must  have  been  previous  to  the 
d  January,  1692,  a  month  before  the  date  of  the 
xtract ;  but  if  we  fix  it  by  the  dates  in  Huygens's 
lanuscript,  we  should  place  it  about  the  29th  No 
ember,    1692,  eighteen    months   previous  to   the 
onversation  between  Collins  and  Huygens.     The 
nanner  in  which  Mr.  Pryme  refers  to  Newton's 
tate  of  mind  is  that  which  is  used  every  day  when 
ve  speak  of  the  loss  of  tranquillity  which  arises 
'om  the  ordinary  afflictions  of  life ;  and  the  meaning 
f  the  passage  amounts  to  nothing  more  than  that 
Newton  was  very  much  troubled  by  the  destruction 
f  his  papers,  and  did  not  recover  his  serenity,  and 
eturn  to  his  usual  occupations,  for  a  month.     The 
ery  phrase  that  "  every  person  thought  he  would 
ave  run  mad"  is  in  itself  a  proof  that  no  such  effect 
as  produced ;  and,  whatever  degree  of  indisposi- 
pn  may  be  implied  in  the  phrase  "he  was  not 
nimself  for  a  month  after,"  we  are  entitled  to  infer 
that  one  month  was  the  period  of  its  duration,  and 
that  previous  to  the  3d  February,  1692,  the  date  of  Mr. 
Pryme's  memorandum,  "Newton  was  himself  again." 
These  facts  and  dates  cannot  be  reconciled  with 
those  in  Huygens's  manuscript.     It  appears  from 
that  document,  that,  so  late  as  May,  1694,  Newton 
had  only  so  far  recovered  his  health  as  to  begin 
to   again  understand  the  Principia.     His    supposed 
[malady,  therefore,  was  in  force   from  the  3d  of 
!  January,   1692,  till  the  month  of  May,   1694, — a 
iperiod  of  more  than  two  years.     Now,  it  is  a  most 
important  circumstance,  which  M.  Biot  ought  to 
have  known,  that  in  the  very  middle  of  this  period, 
S3 


210  SIR   ISAAC   NEWTON. 

Newton  wrote  his  four  celebrated  letters  to  Dr. 
Bentley  on  the  Existence  of  a  Deity, — letters  which 
evince  a  power  of  thought  and  a  serenity  of  mind 
absolutely  incompatible  even  with  the  slightest  ob- 1 
scuration  of  his  faculties.  No  man  can  peruse  these  1 
letters  without  the  conviction  that  their  author  their 
possessed  the  full  vigour  of  his  reason,  and  was< 
capable  of  understanding  the  most  profound  parts) 
of  his  writings.  The  first  of  these  letters  was  writ-! 
ten  on  the  10th  December,  1692,  the  second  on  thej 
17th  January,  1693,  the  third  on  the  25th  February! 
and  the  4th  on  the  llth*  February,  1693.  His  mini 
was,  therefore,  strong  and  vigorous  on  these  four) 
occasions;  and  as  the  letters  were  written  at  thej 
express  request  of  Dr.  Bentley,  who  had  been  ap-f 
pointed  to  deliver  the  lecture  founded  by  Mr.  Boylej 
for  vindicating  the  fundamental  principles  of  natural! 
and  revealed  religion,  we  must  consider  such  a  re-? 
quest  as  showing  his  opinion  of  the  strength  and 
freshness  of  his  friend's  mental  powers. 

In  1692,  Newton,  at  the  request  of  Dr.  Wallis, 
transmitted  to  him  the  first  proposition  of  his  book 
on  quadratures,  with  examples  of 'it  in  first,  second, 
and  third  fluxions. f  These  examples  were  written 
in  consequence  of  an  application  from  his  friend; 
and  the  author  of  the  review  of  the  Commercium 
Epistolicum,  in  which  this  fact  is  quoted,  draws  the 
conclusion,  that  he  had  not  at  that  time  forgotten 
his  method  of  second  fluxions.  It  appears,  also, 
from  the  second  book  of  the  Optics,J  that  in  the 
month  of  June,  1692,  he  had  been  occupied  with  the 
subject  of  haloes,  and  had  made  accurate  observations 
both  on  the  colours  and  the  diameters  of  the  rings 
in  a  halo  which  he  had  then  seen  around  the  sun. 

*  They  are  thus  dated  in  Horsley's  edition  of  Newton's  Works,  the 
fourth  letter  having  an  earlier  date  than  the  third. 

t  See  Newtoni  Opera,  torn.  iv.  p.  480,  and  Wallasii  Opera.  1693,  torn. 
U.  p.  391-396. 

;  Optics,  part  iT.  obs.  13. 


STATE  OF   HIS   MIND.  211 

But  though  these  facts  stand  in  direct  contradic- 
tion to  the  statement  recorded  by  Huygens,  the 
reader  will  be  naturally  anxious  to  know  the  real 
nature  and  extent  of  the  indisposition  to  which  it 
refers.  The  following  letters,*  written  by  Newton 
himself,  Mr.  Pepys,  Secretary  to  the  Admiralty,  and 
Mr.  Millington  of  Magdalene  College,  Cambridge, 
will  throw  much  light  upon  the  subject. 

Newton,  as  will  be  presently  seen,  had  fallen  into 
a  bad  state  of  health  some  time  in  1692,  in  conse- 
quence of  which  both  his  sleep  and  his  appetite 
were  greatly  affected.  About  the  middle  of  Sep- 
tember, 1693,  he  had  been  kept  awake  for  five  nights 
by  this  nervous  disorder,  and  in  this  condition  he 
wrote  the  following  letter  to  Mr.  Pepys : 

"  SIR,  Sept.  13,  1693. 

"  Some  time  after  Mr.  Millington  had  delivered 
your  message,  he  pressed  me  to  see  you  the  next 
time  I  went  to  London.  I  was  averse ;  but  upon 
his  pressing  consented,  before  I  considered  what  I 
did,  for  I  am  extremely  troubled  at  the  embroilment 
I  am  in,  and  have  neither  ate  nor  slept  well  this 
twelvemonth,  nor  have  my  former  consistency  of 
mind.  I  never  designed  to  get  any  thing  by  your 
interest,  nor  by  King  James's  favour,  but  am  now 
sensible  that  I  must  withdraw  from  your  acquaint- 
ance, and  see  neither  you  nor  the  rest  of  my  friends 
any  more,  if  I  may  but  leave  them  quietly.  I  beg 
your  pardon  for  saying  I  would  see  you  again,  and 
rest  your  most  humble  and  most  obedient  servant, 

"  I«.  NEWTON." 

From  this  letter  we  learn,  on  his  own  authority, 
that  his  complaint  had  lasted  for  a  twelvemonth, 
and  that  during  that  twelvemonth  he  neither  ate  nor 
slept  well,  nor  enjoyed  his  former  consistency  of 

*  For  these  letters  I  have  been  indebted  to  the  kindness  of  Lord  Br»F- 
brooke. 


212  SIR   ISAAC   NEWTON 

mind.  It  is  not  easy  to  understand  exactly  what  is 
meant  by  not  enjoying  his  former  consistency  of 
mind  ;  but  whatever  be  its  import,  it  is  obvious  that 
he  must  have  been  in  a  state  of  mind  so  sound  as  to 
enable  him  to  compose  the  four  letters  to  Bentley, 
all  of  which  were  written  during  the  twelvemonth 
here  referred  to. 

On  the  receipt  of  this  letter,  his  friend  Mr.  Pepys 
seems  to  have  written  to  Mr.  Millington  of  Magda- 
lene College  to  inquire  after  Mr.  Newton's  health ; 
but  the  inquiry  having  been  made  in  a  vague  man- 
ner, an  answer  equally  vague  was  returned.  Mr. 
Pepys,  however,  who  seems  to  have  been  deeply 
anxious  about  Newton's  health,  addressed  the  fol- 
lowing more  explicit  letter  to  his  friend  Mr.  Mil- 
lington : — 

"  SIR,  Septemb.  26,  1693. 

"After  acknowledging  your  many  old  favours, 
give  me  leave  to  do  it  a  little  more  particularly  upon 
occasion  of  the  new  one  conveyed  to  me  by  my 
nephew  Jackson.  Though,  at  the  same  time,  I 
must  acknowledge  myself  not  at  the  ease  I  would 
be  glad  to  be  at  in  reference  to  the  excellent  Mr. 
Newton ;  concerning  whom  (methinks)  your  answer 
labours  under  the  same  kind  of  restraint  which  (to 
tell  you  the  truth)  my  asking  did.  For  I  was  loth 
at  first  dash  to  tell  you  that  I  had  lately  received  a 
letter  from  him  so  surprising  to  me  for  the  incon- 
sistency of  every  part  of  it,  as  to  be  put  into  great 
disorder  by  it,  from  the  concernment  I  have  for  him, 
lest  it  should  arise  from  that  which  of  all  mankind  I 
should  least  dread  from  him  and  most  lament  for, — I 
mean  a  discomposure  in  head,  or  mind,  or  both.  Let 
me  therefore  beg  you,  sir,  having  now  told  you  the  true 
ground  of  the  trouble  I  lately  gave  you,  to  let  me 
know  the  very  truth  of  the  matter^  as  far  at  least  as 
comes  within  your  knowledge.  For  I  own  too  great 
an  esteem  for  Mr.  Newton,  as  for  a  public  good,  to 


STATE    OF    HIS    MIND.  213 

1  >e  able  to  let  any  doubt  in  me  of  this  kind  concern- 
ng  him  lie  a  moment  uncleared,  where  I  can  have 
my  hopes  of  helping  it.  I  am,  with  great  truth  and 
respect,  dear  sir,  your  most  humble,  and  most  af- 
fectionate servant, 

"  S.  PEPYS." 

•  To  this  letter  Mr.  Millington  made  the  following 
reply : — 

Coll.  Magd.  Canib. 

"  HONOR'D  SIR,  Sept.  the  30,  1693. 

"  Coming  home  from  a  journey  on  the  28th  instant 
at  night,  I  met  with  your  letter  which  you  were 
)leased  to  honour  me  with  of  the  26th.  I  am  much 
troubled  I  was  not  at  home  in  time  for  the  post, 
that  I  might  as  soon  as  possible  put  you  out  of  your 
generous  payne  that  you  are  in  for  the  worthy  Mr 
Newton.  I  was,  I  must  confess,  very  much  surprised 
at  the  inquiry  you  were  pleased  to  make  by  your 
Lephew  about  the  message  that  Mr.  Newton  made 
-he  ground  of  his  letter  to  you,  for  I  was  very  sure 
I  never  either  received  from  you  or  delivered  to  him 
any  such,  and  therefore  I  went  immediately  to  wayt 
iipon  him,  with  a  design  to  discourse  him  about  the 
(matter,  but,  he  was  out  of  town,  and  since  I  have 
not  seen  him,  till  upon  the  28th  I  met  him  at  Hunt- 
ingdon, where,  upon  his  own  accord,  and  before  I 
had  time  to  ask  him  any  question,  he  told  me  that 
he  had  writt  to  you  a  very  odd  letter,  at  which  he 
was  much  concerned ;  added,  that  it  was  in  a  dis- 
temper that  much  seized  his  head,  and  that  kept  him 
awake  for  above  five  nights  together,  which  upon 
occasion  he  desired  I  would  represent  to  you,  and 
beg  your  pardon,  he  being  very  much  ashamedj  he 
should  be  so  rude  to  a  person  for  whom  he  hath"  so 
great  an  honour.  He  is  now  very  well,  and,  though 
I  fear  he  is  under  some  small  degree  of  melancholy, 
yet  I  think  there  is  no  reason  to  suspect  it  hath  afr 


214  SIR    ISAAC    NEWTON. 

all  touched  his  understanding,  and  I  hope  never  will 
and  so  I  am  sure  all  ought  to  wish  that  love  learning 
or  the  honour  of  our  nation,  which  it  is  a  sign  hoi, 
much  it  is  looked  after,  when  such  a  person  as  Mr.  New 
ton  lyes  so  neglected  by  those  in  power.  And  thus,  hon 
cured  sir,  I  have  made  you  acquainted  with  all  '. 
know  of  the  cause  of  such  inconsistencys  in  th( 
letter  of  so  excellent  a  person ;  and  I  hope  it  wil 
remove  the  doubts  and  fears  you  are,  with  so  mucl 
compassion  and  publickness  of  spirit,  pleased  tc 
entertain  about  Mr.  Newton ;  but  if  I  should  have, 
been  wanting  in  any  thing  tending  to  the  more  fuL 
satisfaction,  I  shall,  upon  the  least  notice,  endeav- 
our to  amend  it  with  all  gratitude  and  truth. 
Honored  sir,  your  most  faithfull  and  most  obedienl 
servant, 

"JOH.  MlLLINGTON." 

Mr.  Pepys  was  perfectly  satisfied  with  this  answer, 
as  appears  from  the  following  letter : — 

"  SIR,  October  3d,  1693. 

"  You  have  delivered  me  from  a  fear  that  indeed 
gave  me  much  trouble,  and  from  my  very  heart  I 
thank  you  for  it ;  an  evil  to  Mr.  Newton  being  what 
every  good  man  must  feel  for  his  own  sake  as  well 
as  his.  God  grant  it  may  stopp  here.  And  for  the 
kind  reflection  hee  has  since  made  upon  his  letter  to 
mee,  I  dare  not  take  upon  mee  to  judge  what  an- 
swer I  should  make  him  to  it,  or  whether  any  or  no ; 
and  therefore  pray  that  you  will  bee  pleased  either 
to  bestow  on  mee  what  directions  you  see  fitt  for 
my  own  guidance  towards  him  in  it,  or  to  say  to 
him  in  my  name,  but  your  own  pleasure,  whatever 
you  think  may  be  most  welcome  to  him  upon  it, 
and  most  expressive  of  my  regard  and  affectionate  es- 
teem of  him,  and  concernment  for  him.  * 
*  *  *  *  Dear  sir,  your 
most  humble  and  most  faithful  servant, 

"  S.  PEPYS," 


CORRESPONDENCE  WITH  LOCKE.      215 

It  does  not  appear  from  the  memoirs  of  Mr. 
Pepys  whether  he  ever  returned  any  answer  to  the 
etter  of  Mr.  Newton  which  occasioned  this  corres- 
pondence ;  but  we  find  that  in  less  than  two  months 
ifter  the  date  of  the  preceding  letter,  an  oppor- 
;unity  occurred  of  introducing  to  him  a  Mr.  Smith, 

o  wished  to  have  his  opinion  on  some  problem  in 
he  doctrine  of  chances.  This  letter  from  Pepys  is 
Jated  November  22d,  1693.  Sir  Isaac  replied  to  it 
i>n  the  26th  November,  and  wrote  to  Pepys  again 
the  16th  December,  1693;  and  in  both  these 
etters  he  enters  fully  into  the  discussion  of  the 
nathematical  question  which  had  been  submitted  to 
lis  judgment.* 

It  is  obvious,  from  Newton's  letter  to  Mr.  Pepys, 
hat  the  subject  of  his  receiving  some  favour  from 
he  government  had  been  a  matter  of  anxiety  with 
u'mself,  and  of  discussion  among  his  friends. f  Mr. 
VTillington  was  no  doubt  referring  to  this  anxiety, 
n  he  represents  Newton  as  an  honour  to  the 
lation,  and  expresses  his  surprise  "  that  such  a  per- 
.on  should  lye  so  neglected  by  those  in  power"  And 
ve  find  the  same  subject  distinctly  referred  to  in 
wo  letters  written  to  Mr.  Locke  during  the  pre- 
jeding  year.  In  one  of  these,  dated  January  26th, 
691-2,  he  says,  "  Being  fully  convinced  that  Mr. 
VIontague,  upon  an  old  grudge  which  I  thought  had 
>een  worn  out,  is  false  to  me,  I  have  done  with  him, 
,nd  intend  to  sit  still,  unless  my  Lord  Monmouth  be 
till  my  friend."  Mr.  Locke  seems  to  have  assured 
lim  of  the  continued  friendship  of  this  nobleman, 
md  Mr.  Newton,  still  referring  to  the  same  topic, 
n  a  letter  dated  February  16th,  1691-2,  remarks, 


"*  These  three  letters  have  been  published  by  Lord  Braybrooke  in  the 
,ife  and  Correspondence  of  Mr.  Pepys. 

t  This  anxiety  will  be  understood  from  the  fact  that,  by  an  order  of 
ouncil  dated  January  28th,  1674-5,  Mr.  Newton  was  excused  from 
laking  the  usual  payments  of  one  shilling  per  week, "  on  account  of  Hia 
ow  circumstances,  as  he  represented." 


'216  SIR   ISAAC   NEWTON. 

I 

"  I  am  very  glad  Lord  Monmouth  is  still  my  friend, 
but  intend  not  to  give  his  lordship  and  you  any  far- 
ther  trouble.  My  inclinations  are  to  sit  still."  In 
a  later  letter  to  Mr.  Locke,  dated  September,  1693, 
and  given  below,  he  asks  his  pardon  for  saying  01 
thinking  that  there  was  a  design  to  sell  him  an 
office.  In  these  letters  Mr.  Newton  no  doubt  re- 
ferred to  some  appointment  in  London  which  he  was 
solicitous  to  obtain,  and  which  Mr.  Montague  and 
his  other  friends  may  have  failed  in  procuring, 
This  opinion  is  confirmed  by  the  letter  of  Mr.  Mon«> 
tague  announcing  to  him  his  appointment  to  the 
wardenship  of  the  mint,  in  which  he  says  that  he  is 
very  glad  he  can  at  last  give  him  good  proof  of  his 
friendship. 

\  In  the  same  month  in  which  Newton  wrote  to  Mr 
Pepys,  we  find  him  in  correspondence  with  Mr 
Locke.  Displeased  with  his  opinions  respecting 
innate  ideas,  he  had  rashly  stated  that  they  struct 
at  the  root  of  all  morality ;  and  that  he  regardec 
the  author  of  such  doctrines  as  a  Hobbist.  Upor 
reconsidering  these  opinions,  he  addressed  the  fol- 
lowing remarkable  letter  to  Locke,  written  three 
days  after  his  letter  to  Mr.  Pepys,  and  conse- 
quently during  the  illness  under  which  he  ther 
.laboured. 

"  SIR, 

"  Being  of  opinion  that  you  endeavoured  to  em- 
broil  me  with  women,  and  by  other  means,  I  was  sc 
much  affected  with  it,  as  that  when  one  told  me  yot 
were  sickly  and  would  not  live,  I  answered,  'twere 
better  if  you  were  dead.  I  desire  you  to  forgive  me 
this  uncharitableness ;  for  I  am  now  satisfied  tha1 
what  you  have  done  is  just,  and  I  beg  your  pardor 
for  my  having  hard  thoughts  of  you  for  it,  and  foi 
representing  that  you  struck  at  the  root  of  morality 


,in  a  principle  you  laid  in  your  book  of  ideas,  ari( 
{designed  to  pursue  in  another  book, ; 


,  and  that  I  tool 


CORRESPONDENCE    WITH   LOCfcE.  217 

you  for  a  Hobbist.*  I  beg  your  pardon  also  for 
saying  or  thinking  that  there  was  a  design  to  sell  me 
an  office,  or  to  embroil  me. — I  am  your  most  hum- 
ble and  unfortunate  servant, 

* "  Is.  NEWTON. 

"  At  the  Bull,  in  Shoreditch,  London, 
Sept.  16th,  1693." 

To  this  letter  Locke  returned  the  following  an- 
swer, so  nobly  distinguished  by  philosophical  mag- 
nanimity and  Christian  charity : — 

"  SIR,  Oates,  Oct.  5/A,  1693. 

"  I  have  been,  ever  since  I  first  knew  you,  so  en 
tirely  and  sincerely  your  friend,  and  thought  you  so 
much  mine,  that  I  could  not  have  believed  what  you 
tell  me  of  yourself  had  I  had  it  from  anybody  else. 
And,  though  I  cannot  but  be  mightily  troubled  that 
you  should  have  had  so  many  wrong  and  unjust 
thoughts  of  me,  yet  next  to  the  return  of  good 
offices,  such  as  from  a  sincere  good-will  I  have  ever 
done  you,  I  receive  your  acknowledgment  of  the 
contrary  as  the  kindest  thing  you  have  done  me, 
since  it  gives  me  hopes  I  have  not  lost  a  friend  I  so 
much  valued.  After  what  your  letter  expresses,  I 
shall  not  need  to  say  any  thing  to  justify  myself  to 
you.  I  shall  always  think  your  own  reflection  on 
my  carriage,  both  to  you  and  all  mankind,  will  suffi- 
ciently do  that.  Instead  of  that,  give  me  leave  to 
assure  you  that  I  am  more  ready  to  forgive  you  than 
you  can  be  to  desire  it ;  and  I  do  it  so  freely  and  fully, 
that  I  wish  for  nothing  more  than  the  opportunity 
to  convince  you  that  I  truly  love  and  esteem  you, 
and  that  I  have  the  same  good-will  for  you  as  if 

*  The  system  of  Hobbes  was  at  this  time  very  prevalent.  According 
to  Dr.  Bentley,  "  the  taverns  and  coffee-houses,  nay,  Westminster  Hall 
and  the  very  churches,  were  full  of  it ;"  and  he  was  convinced  from 
I  personal  observation,  that  "  not  one  English  infidel  in  a  hundred  was 
other  than  a  Hobbist. "— Monk\s  Life  of  Bentley^  p.  31. 

T 


218  SIR  ISAAC    NEWTON. 

nothing  of  this  had  happened.  To  confirm  this  to 
you  more  fully,  I  should  be  glad  to  meet  you  any 
where,  and  the  rather,  because  the  conclusion  of 
your  letter  makes  me  apprehend  it  would  not  be 
wholly  useless  to  you.  But  whether  you  think  it 
fit  or  not,  I  leave  wholly  to  you.  I  shall  always  be 
ready  to  serve  you  to  my  utmost,  in  any  way  you 
shall  like,  and  shall  only  need  your  commands  or 
permission  to  do  it. 

"  My  book  is  going  to  press  for  a  second  edition; 
and,  though  I  can  answer  for  the  design  with  which, 
I  write  it,  yet,  since  you  have  so  opportunely  given : 
me  notice  of  what  you  have  said  of  it,  I  should  take 
it  as  a  favour  if  you  would  point  out  to  me  the 
places  that  gave  occasion  to  that  censure,  that,  by 
explaining  myself  better,  I  may  avoid  being  mis- 
taken by  others,  or  unawares  doing  the  least  preju- 
dice to*  truth  or  virtue.  I  am  sure  you  are  so  much 
a  friend  to  them  both,  that,  were  you  none  to  me,  I 
could  expect  this  from  you.  But  I  cannot  doubt  but 
you  would  do  a  great  deal  more  than  this  for  my 
sake,  who,  after  all,  have  all  the  concern  of  a  friend 
for  you,  wish  you  extremely  well,  and  am,  without 
compliment,  &c."* 


To  this  letter  Newton  made  the  following  reply: — 

"  SIR,  % 

"  The  last  winter,  by  sleeping  too  often  by  my 
fire,  I  got  an  ill  habit  of  sleeping ;  and  a  distemper, 
which  this  summer  has  been  epidemical,  put  me 
farther  out  of  order,  so  that  when  I  wrote  to  you,  I 
had  not  slept  an  hour  a  night  for  a  fortnight  together, 
and  for  five  days  together  not  a  wink.  I  remember 
I  wrote  to  you,  but  what  I  said  of  your  book  I  re- 
member not.  If  you  please  to  send  me  a  transcript 

*  The  draft  of  this  letter  is  endorsed  "  J.  L.  to  I.  Newton." 


CORRESPONDENCE    WITH   LOCKE.  219. 

of  that  passage,  I  will  give  you  an  account  of  it  if  I 
can. — I  am  your  most  humble  servant, 

"Is-  NEWTON. 
"  Cambridge,  Oct.  Sth,  1693." 

Although  the  first  of  these  letters  evinces  the 
existence  of  a  nervous  irritability  which  could  not 
fail  to  arise  from  want  of  appetite  and  of  rest,  yet  it 
is  obvious  that  its  author  was  in  the  full  possession 
of  his  mental  powers.  The  answer  of  Mr.  Locke, 
indeed,  is  written  upon  that  supposition ;  and  it  de- 
serves to  be  remarked,  that  Mr.  Dugald  Stewart, 
who  first  published  a  portion  of  these  letters,  never 
imagines  for  a  moment  that  Newton  was  labouring 
under  any  mental  alienation. 

The  opinion  entertained  by  Laplace,  that  Newton 
devoted  his  attention  to  theology  only  in  the  latter 
Dart  of  his  life,  may  be  considered  as  deriving  some 
countenance  from  the  fact,  that  the  celebrated  gene- 
ral scholium  at  the  end  of  the  second  edition  of  the 
Principia,  published  in  1713,  did  not  appear  in  the 
irst  edition  of  that  work.  This  argument  has  been 
ably  controverted  by  Dr.  J.  C.  Gregory  of  Edinburgh, 
on  the  authority  of  a  manuscript  of  Newton,  which 
seems  to  have  been  transmitted  to  his  ancestor,  Dr. 
David  Gregory,  between  the  years  1687  and  1698. 
i  This  manuscript,  which  consists  of  twelve  folio 
pages  in  Newton's  handwriting,  contains,  in  the 
form  of  additions  and  scholia  to  some  propositions 
in  the  third  book  of  the  Principia,  an  account  of  the 
opinions  of  the  ancient  philosophers  on  gravitation 
and  motion,  and  on  natural  theology,  with  various 
quotations  from  their  works.  Attached  to  this 
manuscript  are  three  very  curious  paragraphs.  The 
first  two  appear  to  have  been  the  original  draught 
of  the  general  scholium  already  referred  to ;  and 
the  third  relates  to  the  subject  of  an  ethereal  me- 
dium, respecting  which  he  maintains  an  opinion 
diametrically  opposite  to  that  which  he  afterward 


220  SIR   ISAAC   NEWTON. 

published  at  the  end  of  his  Optics.*  The  first  para- 
graph  expresses  nearly  the  same  ideas  as  some 
sentences  in  the  scholium  beginning  "  Deus  summus 
est  ens  asternum,  infinitum,  absolute  perfectum  ;"f 
and  it  is  remarkable  that  the  second  paragraph  is 
found  only  in  the  third  edition  of  the  Principia, 
which  appeared  in  1726,  the  year  before  Newton's 
death. 

In  the  middle  of  the  year  1694,  about  the  time 
when  our  author  is  said  to  be  beginning  to  under- 
stand the  Principia,  we  find  him  occupied  with  the 
difficult  and  profound  subject  of  the  lunar  theory. 
In  order  to  procure  observations  for  verifying  the 
equations  which  he  had  deduced  from  the  theory  of 
gravity,  he  paid  a  visit  to  Flamstead,  at  the  Royal 
Observatory  of  Greenwich,  on  the  1st  September, 
1694,  when  he  received  from  him  a  series  of  lunar 
observations.  On  the  7th  of  October  he  wrote  to 
Flamstead  that  he  had  compared  the  observations 
with  his  theory,  and  had  satisfied  himself  that  by 
both  together  "  the  moon's  theory  may  be  reduced 
to  a  good  degree  of  exactness,  perhaps  to  the  exact- 
ness of  two  or  three  minutes."  He  wrote  him  again 
on  the  24th  October,  and  the  correspondence  was 
continued  till  1698,  Newton  making  constant  appli- 
cation for  observations  to  compare  with  his  theory 

*  Dr.  Gregory  concludes  his  account  of  this  manuscript,  which  he  has 
kindly  permitted  me  to  read,  in  the  following  words  :— "  1  do  not  know 
"whether  it  is  true,  as  stated  by  Huygens,  4Newtonurn  incidisse  in  Phre- 
nitim  ;'  but  I  think  every  gentleman  who  examines  this  manuscript  will 
be  of  opinion  that  he  must  have  thoroughly  recovered  from  his  phrenitis 
before  he  wrote  either  the  Commentary  on  the  Opinions  of  the  Ancients, 
or  the  Sketch  of  his  own  Theological  and  Philosophical  Opinions  which 
it  contains." 

t  This  paragraph  is  as  follows : — "  Deum  esse  ens  summe  perfectum 
concedunt  omnes.  Entis  autem  summe  perfecti  Idea  est  ut  sit  substan- 
tia,  una,  simplex,  indivisibilis,  viva  et  vivifica,ubique  semper  necessario 
existens,  summe  intelligens  omnia,  libere  volens  bona,  voluntate  efficiens 
possibilia,  effectibus  nobilioribus  similitudinem  propriam  quantum  fieri 
potest  communicans,  omnia  in  se  continens  tanquam  eorurn  principium. 
et  locus,  omnia  per  presentiam  substantialem  cernens  et  regens,  et  cum 
rebus  omnibus,  secundum  leges  accuratas  ut  naturae  totius  fundamen* 
turn  et  causa  constanter  co-operans,  nisi  ubi  aliter  agere  bonum  eat." 


CORRESPONDENCE  WITH  FLAMSTEAD.    221 

of  the  planetary  motions ;  while  Flamstead,  not  suffi- 
ciently aware  of  the  importance  of  the  inquiry,  re- 
ceived his  requests  as  if  they  were  idle  intrusions  in 
which  the  interests  of  science  were  but  slightly  con- 
cerned.* 

In  reviewing  the  details  which  we  have  now  given 
respecting  the  health  and  occupations  of  Newton 
from  the  beginning  of  1692  till  1695,  it  is  impossible 
to  draw  any  other  conclusion  than  that  he  possessed 
a  sound  mind,  and  was  perfectly  capable  of  carrying 
on  his  mathematical,  his  metaphysical,  and  his  astro- 
nomical inquiries.  His  friend  and  admirer,  Mr. 
Pepys,  residing  within  fifty  miles  of  Cambridge,  had 
never  heard  of  his  being  attacked  with  any  illness 
till  he  inferred  it  from  the  letter  to  himself  written 
in  September,  1693.  Mr.  Millington,  who  lived  in 
the  same  university,  had  been  equally  unacquainted 
with  any  such"  attack,  and,  after  a  personal  inter- 
view with  Newton,  for  the  express  purpose  of  ascer- 
taining the  state  of  his  health,  he  assures  Mr.  Pepys 
"  that  he  is  very  well, — that  he  fears  he  is  under 
some  small  degree  of  melancholy,  but  that  there  is 

*  The  following  extract,  characteristic  of  Flamstead's  manner,  is  from 
a  letter  to  Newton  dated  January  6,  1698-9. 

"Upon  hearing  occasionally  that  you  had  sent  a  letter  to  Dr.  Wallis 
about  the  paraUax  of  the  fixed  stars  to  be  printed,  and  that  you  had  men- 
tioned me  therein  with  respect  to  the  theory  of  the  moon,  I  was  con- 
cerned to  be  publicly  brought  upon  the  state  about  what,  perhaps,  will 
never  be  fitted  for  the  public,  and  thereby  the  world  piit  into  an  expecta 
tion  of  what  perhaps  they  are  never  likely  to  have.  I  do  not  love  to  be 
printed  upon  every  occasion,  much  less  to  be  dunned  and  teased  by 
foreigners  about  mathematical  things,  or  to  be  thought  by  your  own  people 
to  be  trifling  away  my  time  when  I  should  be  about  the  king's  business." 
On  the  first  of  the  above  passages  in  italics  Flamstead  has  the  follow- 
ing memorandum : — "  When  Mr.  Halley  boasts  'tis  done,  and  given  to 
him  as  a  secret,  tells  the  Society  so  and  foreigners.'  In  the  second  pas- 
sage in  italics,  Mr.  Flamstead  refers,  in  a  note,  to  Mr.  Colson's  letter  to 
him,  in  which  he  seems  to  have  represented  practical  astronomy  as 
trifling.  Mr.  Flamstead  adds,  "  Was  Mr.  Newton  a  trifler  when  he  read 
mathematics  for  a  salary  at  Cambridge  :  surely,  then,  astronomy  is  of 
some  good  use,  though  his  place  be  more  beneficial."  For  these  extracts 
from  the  original  manuscript  in  the  collection  of  Corpus  Christi  College, 
Oxford,  I  have  been  indebted  to  the  kindness  of  Professor  Rigaud  of 
Oxford. 


222  SIR   ISAAC   NEWTON. 

no  reason  to  suspect  that  it  hath  at  all  touched  his 
understanding." 

During  this  period  of  bodily  indisposition,  his 
mind,  though  in  a  state  of  nervous  irritability,  and 
disturbed  by  want  of  rest,  was  capable  of  putting 
forth  its  highest  powers.  At  the  request  of  Dr. 
Wallis  he  drew  up  an  example  of  one  of  his  pro- 
positions on  the  quadrature  of  curves  in  second 
fluxions.  He  composed,  at  the  desire  of  Dr.  Bentley, 
his  profound  and  beautiful  letters  on  the  existence 
of  the  Deity.  He  was  requested  by  Locke  to  re- 
consider his  opinions  on  the  subject  of  innate  ideas ; 
and  we  find  him  grappling  with  the  difficulties  of  the 
lunar  theory. 

But  with  all  these  proofs  of  a  vigorous  mind,  a 
diminution  of  his  mental  powers  has  been  rashly 
inferred  from  the  cessation  of  his  great  discoveries, 
and  from  his  unwillingness  to  enter  upon  new  in- 
vestigations. The  facts,  however,  here  assumed 
are  as  incorrect  as  the  inference  which  is  drawn 
from  them.  The  ambition  of  fame  is  a  youthful 
passion,  which  is  softened,  if  not  subdued,  by  age. 
Success  diminishes  its  ardour,  and  early  pre-emi- 
nence often  extinguishes  it.  Before  the  middle 
period  of  life  Newton  was  invested  with  all  the 
insignia  of  immortality ;  but  endowed  with  a  native 
humility  of  mind,  and  animated  with  those  hopes 
which  teach  us  to  form  an  humble  estimate  of  human 
greatness,  he  was  satisfied  with  the  laurels  which 
he  had  won,  and  he  sought  only  to  perfect  and  com- 
plete his  labours.  His  mind  was  principally  bent  on 
the  improvement  of  the  Principia ;  but  he  occasion- 
ally diverged  into  new  fields  of  scientific  research, 
— he  solved  problems  of  great  difficulty  which  had 
been  proposed  to  try  his  strength, — and  he  devoted 
much  of  his  time  to  profound  inquiries  in  chronology 
and  in  theological  literature. 

The  powers  of  his  mind  were  therefore  in  full 
requisition;   and,  when  we  consider  that  he  was 


MERITS   NEGLECTED.  223 

called  to  the  discharge  of  high  official  functions 
which  forced  him  into  public  life,  and  compelled 
him  to  direct  his  genius  into  new  channels,  we  can 
scarcely  be  surprised  that  he  ceased  to  produce  any 
original  works  on  abstract  science.  In  the  direc- 
tion of  the  affairs  of  the  mint,  and  of  the  Royal  So- 
ciety, to  which  we  shall  now  follow  him,  he  found 
ample  occupation  for  his  time ;  while  the  leisure  of 
his  declining  years  was  devoted  to  those  exalted 
studies  in  which  philosophy  yields  to  the  supremacy 
of  faith,  and  hope  administers  to  the  aspirations  of 
genius. 


CHAPTER  XIV. 

No  Mark  of  National  Gratitude  conferred  upon  Newton — Friendship 
between  him  and  Charles  Montague,  afterward  Earl  of  Halifax — Mr 
Montague  appointed  Chancellor  of  the  Exchequer  in  1694 — He  resolves 
upon  a  Recoinage — Nominates  Mr.  Newton  Warden  of  the  Mint  in 
1695 — Mr.  Newton  appointed  Master  of  the  Mint  in  1699 — Notice  of 
the  Earl  of  Halifax— Mr.  Newton  elected  Associate  of  the  Academy 
of  Sciences  in  1699 — Member  for  Cambridge  in  1701 — and  President 
of  the  Royal  Society  in  1703 — Queen  Anne  confers  upon  him  the 
Honour  of  Knighthood  in  1705 — Second  Edition  of  the  Principia, 
edited  by  Cotes — His  Conduct  respecting  Mr.  Ditton's  Method  of  find- 
ing the  Longitude. 

HITHERTO  we  have  viewed  Newton  chiefly  as  a 
philosopher  leading  a  life  of  seclusion  within  the 
walls  of  a  college,  and  either  engaged  in  the  duties 
of  his  professorship,  or  ardently  occupied  in  mathe- 
matical and  scientific  inquiries.  He  had  now  reached 
the  fifty-third  year  of  his  age,  and  while  those  of  his 
own  standing  at  the  university  had  been  receiving 
high  appointments  in  the  church,  or  lucrative  offices 
in  the  state,  he  still  remained  without  any  mark  of 
the  respect  or  gratitude  of  his  country.  All  Europe 
indeed  had  been  offering  incense  to  his  name,  and 


224  SIR   ISAAC   NEWTON. 

Englishmen  themselves  boasted  of  him  as  the  pride 
of  their  country  and  the  ornament  of  their  species, 
but  he  was  left  in  comparative  poverty,*  with  no 
other  income  than  the  salary  of  his  professorship, 
eked  out  with  the  small  rental  of  his  paternal  in- 
heritance. Such  disregard  of  the  highest  genius, 
dignified  by  the  highest  virtue,  could  have  taken 
place  only  in  England,  and  we  should  have  ascribed 
it  to  the  turbulence  of  the  age  in  which  he  lived, 
had  we  not  seen,  in  the  history  of  another  century, 
that  the  successive  governments  which  preside  over 
the  destinies  of  our  country  have  never  been  able 
either  to  feel  or  to  recognise  the  true  nobility  of 
genius. 

Among  his  friends  at  Cambridge  Newton  had  the 
honour  of  numbering  Charles  Montague,  grandson 
of  Henry  Earl  of  Manchester,  a  young  man  of  high 
promise,  and  every  way  worthy  of  his  friendship. 
Though  devoted  to  literary  pursuits,  and  twenty 
years  younger  than  Newton,  he  cherished  for  the 
philosopher  all  the  veneration  of  a  disciple,  and  his 
affection  for  him  gathered  new  strength  as  he  rose 
to  the  highest  honours  and  offices  of  the  state.  In 
the  year  1684  we  find  him  co-operating  with  Newton 
in  the  establishment  of  a  philosophical  society  at 
Cambridge ;  but  though  both  of  them  had  made  per- 
sonal application  to  different  individuals  to  become 
members,  yet  the  plan  failed,  from  the  want,  as 
Newton  expresses  it,  of  persons  willing  to  try  ex- 
periments. 

Mr.  Montague  sat  along  with  Newton  in  the  con- 
vention parliament,  and  such  were  the  powers  which 
he  displayed  in  that  assembly  as  a  public  speaker, 
that  he  was  appointed  a  commissioner  of  the  treasury, 
and  soon  afterward  a  privy  counsellor.  In  these 
situations  his  talents  and  knowledge  of  business 
were  highly  conspicuous,  and  in  1694  he  was  ap« 

*  See  page  215,  note. 


WARDEN   OF   THE    MINT.  225 

pointed  chancellor  of  the  exchequer.  The  current 
coin  of  the  nation  having  been  adulterated  and  de- 
based, one  of  his  earliest  designs  was  to  recoin  it 
and  restore  it  to  its  intrinsic  value.  This  scheme, 
however,  met  with  great  opposition.  It  was  char- 
acterized as  a  wild  project,  unsuitable  to  a  period 
of  war,  as  highly  injurious  to  the  interests  of  com- 
merce, and  as  likely  to  sap  the  foundation  of  the 
government.  But  he  had  weighed  the  subject  too 
deeply,  and  had  intrenched  himself  behind  opinions 
too  impartial  and  too  well-founded,  to  be  driven  from 
a  measure  which  the  best  interests  of  his  country 
seemed  to  require. 

The  persons  whom  Mr.  Montague  had  consulted 
about  the  recoinage  were  Newton,  Locke,  and  Hal- 
ley,  and  in  consequence  of  Mr.  Overton,  the  warden 
of  the  mint,  having  been  appointed  a  commissioner 
of  customs,  he  embraced  the  opportunity  which  was 
thus  offered  of  serving  his  friend  and  his  country  by 
recommending  Newton  to  that  important  office. 
The  notice  of  this  appointment  was  conveyed  in  the 
following  letter  to  Newton. 

"  SIR,  London,  19th  March,  1695. 

"  1  am  very  glad  that,  at  last,  I  can  give  you  a 

food  proof  of  my  friendship,  and  the  esteem  the 
ing  has  of  your  merits.  Mr.  Overton,  the  warden 
of  the  mint,  is  made  one  of  the  commissioners  of 
the  customs,  and  the  king  has  promised  me  to  make 
Mr.  Newton  warden  of  the  mint.  The  office  is  the 
most  proper  for  you.  'Tis  the  chief  office  in  the  mint, 
'tis  worth  five  or  six  hundred  pounds  per  annum,  and 
has  not  too  much  business  to  require  more  attendance 
than  you  can  spare.  T  desire  that  you  will  come  up 
as  soon  as  you  can,  and  I  will  take  care  of  your 
warrant  in  the  meantime.  Let  me  see  you  as  soon 
as  you  come  to  town,  that  I  may  carry  you  to  kiss 
the  king's  hand.  I  believe  you  may  have  a  lodging 
near  me. — I  am,  &c.  CHARLES  MONTAGUE*" 


226  SIR   ISAAC   NEWTON. 

In  this  new  situation  the  mathematical  and  chy- 
mical  knowledge  of  our  author  was  of  great  service 
to  the  nation,  and  he  became  eminently  useful  in 
carrying  on  the  recoinage,  which  was  completed  in 
the  short  space  of  two  years.  In  the  year  1699,  he 
was  promoted  to  the  mastership  of  the  mint, — an 
office  which  was  worth  twelve  or  fifteen  hundred 
pounds  per  annum,  and  which  he  held  during  the 
remainder  of  his  life.  In  this  situation  he  wrote  an 
official  report  on  the  Coinage,  which  has  been  pub- 
lished ;  and  he  drew  up  a  table  of  Assays  of  Foreign 
Coins,  which  is  printed  at  the  end  of  Dr.  Arbuthnot's 
Tables  of  Ancient  Coins,  Weights,  and  Measures, 
which  appeared  in  1727. 

While  our  author  filled  the  inferior  office  of  warden 
of  the  mint,  he  retained  his  professorship  at  Cam- 
bridge ;  but  upon  his  promotion  in  1699,  he  appointed 
Mr.  Whiston  to  be  his  deputy,  with  all  the  emolu- 
ments of  the  office ;  and  when  he  resigned  the  chair 
in  1703,  he  succeeded  in  getting  him  nominated  his 
successor. 

The  appointment  of  Newton  to  the  mastership  of 
the  mint  must  have  been  peculiarly  gratifying  to 
the  Royal  Society,  and  it  was  probably  from  a  feel- 
ing of  gratitude  to  Mr.  Montague,  as  much  as  from 
a  regard  for  his  talents,  that  this  able  statesman  was 
elected  president  of  that  learned  body  on  the  30th 
November,  1695.  This  office  he  held  for  three 
years,  and  on  the  30th  January,  1697,  Newton  had 
the  satisfaction  of  addressing  to  him  his  solution  of 
the  celebrated  problems  proposed  by  John  Bernouilli. 

This  accomplished  nobleman  was  created  Earl  of 
Halifax  in  1700,  and  after  the  death  of  his  first  wife 
he  conceived  a  strong  attachment  for  Mrs.  Catharine 
Barton,  the  widow  of  Colonel  Barton,  and  the  niece 
of  Newton.  This  lady  was  young,  gay,  and  beau- 
tiful, and  though  she  did  not  escape  the  censures  of 
her  contemporaries,  she  was  regarded  by  those  who 
knew  her  as  a  woman  of  strict  honour  and  virtue. 


PRESIDENT    OF   THE   ROYAL   SOCIETY.       227 

We  are  not  acquainted  with  the  causes  which  pre- 
vented her  union  with  the  Earl  of  Halifax,  but  so 
great  was  the  esteem  and  affection  which  he  bore 
her,  that  in  the  will  in  which  he  left  100/.  to  Mr. 
Newton,  he  bequeathed  to  his  niece  a  very  large 
portion  of  his  fortune.  This  distinguished  states- 
man died  in  1715,  in  the  fifty-fourth  year  of  his  age. 
Himself  a  poet  and  an  elegant  writer,  he  was  the 
liberal  patron  of  genius,  and  he  numbered  among 
his  intimate  friends  Congreve,  Halley,  Prior,  Tickell, 
Steele,  and  Pope.  His  conduct  to  Newton  will  be 
for  ever  remembered  in  the  annals  of  science.  The 
sages  of  every  nation  and  of  every  age  will  pronounce 
with  affection  the  name  of  Charles  Montague,  and 
the  persecuted  science  of  England  will  continue  to 
deplore  that  he  was  the  first  and  the  last  English 
minister  who  honoured  genius  by  his  friendship  and 
rewarded  it  by  his  patronage. 

The  elevation  of  Mr.  Newton  to  the  highest  offices 
in  the  mint  was  followed  by  other  marks  of  honour. 
The  Royal  Academy  of  Sciences  at  Paris  having 
been  empowered  by  a  new  charter  granted  in  1699, 
to  admit  a  very  small  number  of  foreign  associates, 
Newton  was  elected  a  member  of  that  distinguished 
body.  In  the  year  1701,  on  the  assembling  of  a  new 
parliament,  he  was  re-elected  one  of  the  members 
for  the  University  of  Cambridge.*  In  1703  he  was 
chosen  President  of  the  Royal  Society  of  London, 
anJ;  he  was  annually  re-elected  to  this  office  during 
the  remaining  twenty-five  years  of  his  life.  On  the 
16th  of  April,  1705,  when  Queen  Anne  was  living  at 
the  royal  residence  of  Newmarket,  she  went  with 
Prince  George  of  Denmark  and  the  rest  of  the  court 
to  visit  the  University  of  Cambridge.  After  the 
meeting  of  the  Regia  Consilia,  her  majesty  held  a 

*  The  candidates  in  1701  were  as  follows ; 
Mr.  Henry  Boyle,  afterward  Lord  Carleton,  180  >     Both  of  Trinity 

Mr.  Newton 161  j  College. 

Mr.  Hammond ....    64 


228  SIR    ISAAC    NEWTON. 

court  at  Trinity  Lodge,  the  residence  of  Dr.  Bentley, 
then  master  of  Trinity ;  where  the  honour  of  knight- 
hood was  conferred  upon  Mr.  Newton,  Mr.  John  Ellis, 
the  vice-chancellor,  and  Mr.  James  Montague,  the 
university  counsel.* 

On  the  dissolution  of  the  parliament,  which  took 
place  in  1705,  Sir  Isaac  was  again  a  candidate  for 
the  representation  of  the  University,^  but  notwith- 
standing the  recent  expression  of  the*  royal  favour, 
he  lost  his  election  by  .a  very  great  majority.! 
This  singular  result  was  perhaps  owing  to  the  loss 
of  that  personal  influence  which  his  residence  in  the. 
university  could  not  fail  to  command,  though  it  is 
more  probable  that  the  ministry  preferred  the  candi- 
dates of  a  more  obsequious  character,  and  that  the 
electors  looked  for  advantages  which  Sir  Isaac  New 
ton  was  not  able  to  obtain  for  them. 

Although  the  first  edition  of  the  Principiahad  been 
for  some  time  sold  off,  and  copies  of  it  had  become 
extremely  rare,  yet  Sir  Isaac's  attention  was  so 
much  occupied  with  his  professional  avocations  that 
he  could  not  find  leisure  for  preparing  a  new  edition. 
Dr.  Bentley,  who  had  repeatedly  urged  him  to  this 
task,  at  last  succeeded,  by  engaging  Roger  Cotes, 
Plumian  Professor  of  Astronomy  at  Cambridge,  to 
superintend  its  publication  at  the  university  press. 
In  June,  1709,  Sir  Isaac  committed  this  important 
trust  to  his  young  friend ;  and  about  the  middle1  of 
July  he  promised  to  send  him  in  the  course  of  a  fort- 
night his  own  revised  copy  of  the  work.  Business, 
however,  seems  to  have  intervened,  and  Mr.  Cotes 
was  obliged  to  remind  Sir  Isaac  of  his  promise,  which 
he  did  in  the  following  letter : — 

*  The  banquet  which  was  on  this  occasion  given  in  the  college  hall 
to  the  royal  visiter  seems  to  have  cost  about  1000Z.,  and  the  university 
was  obliged  to  borrow  500/.,  to  defray  the  expense  of  it.—Monk'i  Lift 
of  Bentley,  p.  143,  144. 
t  The  candidates  in  1705  were  as  follows : 

The  Hon.  Arthur  Annesley  182 
Hon.  Dixie  Windsor  .  170 
Mr,  Godolphin  .  .  .162 
Sir  Isaac  Newton  .  .  117 


SECOND   EDITION   OF   THE    PRINCIPIA.         229 

"  SIR,  Cambridge,  Aug.  ISth,  1709. 

"  The  earnest  desire  I  have  to  see  a  new  edition 
f  your  Principia  makes  me  somewhat  impatient 
ill  we  receive  your  copy  of  it,  which  you  were 
leased  to  promise  me  about  the  middle  of  last  month 
rou  would  send  down  in  about  a  fortnight's  time. 
3  hope  you  will  pardon  me  for  this  uneasiness,  from 
which  I  cannot  free  myself,  and  for  giving  you  this 
;rouble  to  let  you  know  it.    I  have  been  so  much 
obliged  by  yourself  and  by  your  book,  that  (I  desire 
you  to  believe  me)  I  think  myself  bound  in  gratitude 
;o  take  all  the  care  I  possibly  can  that  it  shall  be 
correct. — Your  obliged  servant, 

"  ROGER  COTES. 

"  For  Sir  Isaac  Newton,  at  his  house  in 

Jermyn-street,  near  St.  James's 

Church,  Westminster." 

This  was  the  first  letter  of  that  celebrated  corres- 
>ondence,  consisting  of  nearly  three  hundred  letters, 
n  which  Sir  Isaac  and  Mr.  Cotes  discussed  the  various 
mprovements  which  were  thought  necessary  in  a 
[lew  edition  of  the  Principia.  This  valuable  collec- 
tion of  letters  is  preserved  in  the  library  of  Trinity 
College  ;  and  we  cannot  refrain  from  repeating  the 
wish  expressed  by  Dr.  Monk,  "  that  one  of  the  many 
accomplished  Newtonians  who  are  resident  in  that 
society  would  favour  the  world  by  publishing  the 
whole  collection." 

When  the  work  was  at  last  printed,  Mr.  Cotes  ex- 
f  >ressed  a  wish  that  Dr.  Bentley  should  write  the  pre- 
face to  it,  but  it  was  the  opinion  both  of  Sir  Isaac 
and  Dr.  Bentley  that  the  preface  should  come  from 
|the  pen  of  Mr.  Cotes  himself.  This  he  accordingly 
undertook;  but  previous  to  its  execution  he  ad- 
pressed  the  following  letter  to  Dr.  Bentley,  in  order 
to  learn  from  Sir  Isaac  the  particular  view  with 
which  it  should  be  written. 
U 


230  SIR  ISAAC   NEWTON. 

"  SIR,  March  10M,  1712-13. 

"  I  received  what  you  wrote  to  me  in  Sir  Isaac's 
letter.  I  will  set  about  the  index  in  a  day  or  two. 
As  for  the  preface,  I  should  be  glad  to  know  from 
Sir  Isaac  with  what  view  he  thinks  proper  to  have 
it  written.  You  know  the  book  has  been  received 
abroad  with  some  disadvantage,  and  the  cause  of  it 
may  be  easily  guessed  at.  The  Commercium  Episto- 
licum,  lately  published  by  order  of  the  Royal  Society, 
gives  such  indubitable  proofs  of  Mr.  Leibnitz's  want  of 
candour,  that  I  shall  not  scruple  in  the  least  to  speak 
out  the  full  truth  of  the  matter,  if  it  be  thought 
convenient.  There  are  some  pieces  of  his  looking 
this  way  which  deserve  a  censure,  as  his  Tentamen 
de  motuum  c&lestium  causis.  If  Sir  Isaac  is  willing 
that  something  of  this  nature  may  be  done,  I  should 
be  glad  if,  while  I  am  making  the  index,  he  would 
consider  of  it,  and  put  down  a  few  notes  of  what  he 
thinks  most  material  to  be  insisted  on.  This  I  say 
upon  supposition  that  I  write  the  preface  myself. 
But  I  think  it  will  be  much  more  advisable  that  you, 
or  he,  or  both  of  you  should  write  it  while  you  are 
in  town.  You  may  depend  upon  it  I  will  own  it, 
and  defend  it  as  well  as  I  can,  if  hereafter  there  be 
occasion. — I  am  sir,  &c." 

We  are  not  acquainted  with  the  instructions  which 
were  given  to  Mr.  Cotes  in  consequence  of  this  ap- 
plication; but  it  appears  from  the  preface  itself, 
which  contains  a  long  and  able  summary  of  the  New- 
tonian philosophy,  that  Sir  Isaac  had  prohibited  any 
personal  reference  to  the  conduct  of  Leibnitz. 

The  general  preface  is  dated  12th  May,  1713,  and 
in  a  subsidiary  preface  of  only  a  few  lines,  dated 
March  28th,  i7I3,  Sir  Isaac  mentions  the  leading 
alterations  which  had  been  made  in  this  edition. 
The  determination  of  the  forces  by  which  bodies 
may  revolve  in  given  orbits  was  simplified  and  en- 
larged. The  theory  of  the  resistance  of  fluids  was 


LONGITUDE    AT   SEA.  231 

more  accurately  investigated,  and  confirmed  by  new 
experiments.  The  theory  of  the  moon  and  the  pre- 
cession of  the  equinoxes  were  more  fully  deduced 
from  their  principles ;  and  the  theory  of  comets  was 
confirmed  by  several  examples  of  their  orbits  more 
accurately  computed. 

In  the  year  1714,  several  captains  and  owners  of 
merchant  vessels  petitioned  the  House  of  Commons 
to  consider  the  propriety  of  bringing  in  a  bill  to 
reward  inventions  for  promoting  the  discovery  of 
the  longitude  at  sea.  A  committee  was  appointed  to 
investigate  the  subject,  and  Mr.  Ditton  and  Mr. 
Whiston,  having  thought  of  a  new  method  of  finding 
the  longitude,  submitted  it  to  the  committee.  Four 
members  of  the  Royal  Society,  viz.  Sir  Isaac  New- 
ton, Dr.  Halley,  Mr.  Cotes,  and  Dr.  Clarke,  were 
examined  on  the  subject,  along  with  Mr.  Ditton  and 
Mr.  Whiston.  The  last  three  of  these  philosophers 
stated  their  opinions  verbally.  Mr.  Cotes  considered 
the  proposed  scheme  as  correct  in  theory  and  on 
shore,  and  both  he  and  Dr.  Halley  were  of  opinion 
that  expensive  experiments  would  be  requisite. 
Newton,  when  called  upon  for  his  opinion,  read  the 
following  memorandum,  which  deserves  to  be  re- 
corded. 

"  For  determining  the  longitude  at  sea  there  have 
been  several  projects,  true  in  theory,  but  difficult  to 
execute. 

"  1.  One  is  by  a  watch  to  keep  time  exactly;  but 
by  reason  of  the  motion  of  the  ship,  the  variation 
of  heat  and  cold,  wet  or  dry,  and  the  difference  of 
gravity  in  different  latitudes,  such  a  watch  hath  not 
yet  been  made. 

"  2.  Another  is  by  the  eclipses  of  Jupiter's  satel- 
lites; but  by  reason  of  the  length  of  telescopes 
requisite  to  observe  them,  and  the  motion  of  a  ship 
at  sea,  those  eclipses  cannot  yet  be  there  observed. 

"  3.  A  third  is  by  the  place  of  the  moon  ;  but  her 
theory  is  not  yet  exact  enough  for  that  purpose ;  it 


232  SIR  ISAAC   NEWTON. 

is  exact  enough  to  determine  the  longitude  within 
two  or  three  degrees,  but  not  within  a  degree. 

"  4.  A  fourth  is  Mr.  Ditton's  project,  and  this  is 
rather  for  keeping  an  account  of  the  longitude  at 
sea  than  for  rinding  it,  if  at  any  time  it  should  be 
lost,  as  it  may  easily  be  in  cloudy  weather.  How  far 
this  is  practicable,  and  with  what  charge,  they  that 
are  skilled  in  sea  affairs  are  best  able  to  judge.  In 
sailing  by  this  method,  whenever  they  are  to  pass 
over  very  deep  seas,  they  must  sail  due  east  or  west ; 
they  must  first  sail  into  the  latitude  of  the  next  place 
to  which  they  are  going  beyond  it,  and  then  keep 
due  east  or  west  till  they  come  at  that  place.  In 
the  first  three  ways  there  must  be  a  watch  regulated 
by  a  spring,  and  rectified  every  visible  sunrise  and 
sunset,  to  tell  the  hour  of  the  day  or  night.  In  the 
fourth  way  such  a  watch  is  not  necessary.  In  the 
first  way  there  must  be  two  watches,  this  and  the 
other  above  mentioned.  In  any  of  the  first  three 
ways,  it  may  be  of  some  service  to  find  the  longitude 
within  a  degree,  and  of  much  more  service  to  find  it 
within  forty  minutes,  or  half  a  degree  if  it  may,  and 
the  success  may  deserve  rewards  accordingly.  In 
the  fourth  way,  it  is  easier  to  enable  seamen  to 
know  their  distance  and  bearing  from  the  shore  40, 
60,  or  80  miles  off,  than  to  cross  the  seas ;  and  some 
part  of  the  reward  may  be  given  when  the  first  is 
performed  on  the  coast  of  Great  Britain  for  the  safety 
of  ships  coming  home  ;  and  the  rest  when  seamen 
shall  be  enabled  to  sail  to  an  assigned  remote  har- 
bour without  losing  their  longitude  if  it  may  be." 

The  committee  brought  up  their  report  on  the  llth 
June,  and  recommended  that  a  bill  should  be  intro- 
duced into  parliament  for  the  purpose  of  rewarding 
inventions  or  discoveries  connected  with  the  deter- 
mination of  the  longitude.  The  bill  passed  the 
House  of  Commons  on  the  3d  July,  and  was  agreed 
to  by  the  Lords  on  the  8th  of  the  same  month.* 
*  Journals  of  the  House  of  Commons,  voL  xvii.  p.  677, 716 


LONGITUDE   AT    SEA.  238 

In  giving  an  account  of  this  transaction,*  Mr. 
Whiston  states,  that  nobody  understood  Sir  Isaac's 
paper,  and  that  after  sitting  down  he  obstinately 
kept  silence,  though  he  was  much  pressed  to  explain 
himself  more  distinctly.  At  last,  seeing  that  the 
scheme  was  likely  to  be  rejected,  Whiston  ventured 
to  say  that  Sir  Isaac  did  not  wish  to  explain  more 
through  fear  of  compromising  himself,  but  that  he 
really  approved  of  the  plan.  Sir  Isaac,  he  goes  on 
to  say,  repeated  word  for  word  what  Whiston  had 
said.  This  is  the  part  of  Mr.  Newton's  conduct 
which  M.  Biot  has  described  as  puerile,  and  "  tend- 
ing to  confirm  the  fact  of  the  aberration  of  his  intel- 
lect in  1693."  Before  we  can  admit  such  a  censure 
we  must  be  satisfied  with  the  correctness  of  Whis- 
km's  statement.  Newton's  paper  is  perfectly  intel- 
ligible, and  we  may  easily  understand  how  he  might 
[lave  approved  of  Mr.  Ditton's  plan  as  ingenious  and 
practicable  under  particular  circumstances,  though 
he  did  not  think  it  of  that  paramount  importance 
which  would  have  authorized  the  House  of  Com- 
mons to  distinguish  it  by  a  parliamentary  reward. 
The  conflict  between  public  duty  and  a  disposition 
to  promote  the  interests  of  Mr.  Whiston  and  Mr. 
Ditton  was  no  doubt  the  cause  of  that  embarrass* 
ment  of  manner  which  the  former  of  these  mathe- 
maticians has  so  unkindly  brought  before  the  public. 

*  Whiston's  "  Longitude  Discovered."    Lond  1738. 

us 


234  SIR  ISAAC   NEWTON. 


CHAPTER  XV. 

Respect  in  which  Newton  was  held  at  the  Court  of  George  L —  The  Prtn* 
cess  of  Wales  delighted  with  his  Conversation — Leibnitz  et^.eavourtf 
to  prejudice  the  Princess  against  Sir  Isaac  and  Locker-Controversy 
occasioned  by  his  Conduct—  The  Princess  obtains  a  Manuscript  Ab» 
stract  of  his  System  of  Chronology — The  Abb4  Conti  is,  at  her  request, 
allowed  to  take  a  Copy  of  it  on  the  promise  of  Secresy — He  prints  it 
surreptitiously  in  French,  accompanied  with  a  Refutation  by  M.  Freret 
-~Sir  Isaac's  Defence  of  his  System — Father  Sonciet  attacks  it — and 
ts  answered  by  Dr.  Halley~Sir  Isaac's  larger  Work  on  Chronology 
published  after  his  Death — Opinions  respecting  it — Sir  Isaac's  Paper 
on  the  Form  of  the  most  ancient  Year. 

ON  the  accession  of  George  I.  to  the  British  throne 
in  1714,  Sir  Isaac  Newton  became  an  object  of  in- 
terest at  court.  His  high  situation  under  govern- 
ment, his  splendid  reputation,  his  spotless  charac- 
ter, and,  above  all,  his  unaffected  piety  attracted 
tfcs  attention  of  the  Princess  of  Wales,  afterward 
queen-consort  to  George  II.  This  lady,  who  pos- 
sessed a  highly  cultivated  mind,  derived"  the  greatest 
pleasure  from  conversing  with  Newton  and  corres- 
ponding with  Leibnitz.  In  all  her  difficulties,  she 
received  from  Sir  Isaac  that  information  and  assist- 
ance which  she  had  elsewhere  sought  in  vain,  and 
she  was  often  heard  to  declare  in  public  that  she 
thought  herself  fortunate  in  living  at  a  time  which 
enabled  her  to  enjoy  the  conversation  of  so  great  a 
genius.  But  while  Newton  was  thus  esteemed  by 
the  house  of  Hanover,  Leibnitz,  his  great  rival,  en- 
deavoured to  weaken  and  undermine  his  influence. 
In  his  correspondence  with  the  princess,  he  repre- 
sented the  Newtonian  philosophy,  not  only  as  phy- 
sically false,  but  as  injurious  to  the  interests  of 
religion.  He  asserted  that  natural  religion  was 
rapidly  declining  in  England,  and  he  supported  this 
position  by  referring  to  the  works  of  Locke,  and  to 


CHRONOLOGY.  235 

the  beautiful  and  pious  sentiments  contained  in  the 
28th  query  at  the  end  of  the  Optics.  He  represented 
;he  principles  of  these  great  men  as  precisely  the 
same  with  those  of  the  materialists,  and  thus  endea- 
•oured  to  degrade  the  character  of  English  philoso- 
phers. 

These  attacks  of  Leibnitz  became  subjects  of  con- 
•ersation  at  court,  and  when  they  reached  the  ear  of 
he  king,  his  majesty  expressed  his  expectation  that 
Sir  Isaac  Newton  would  draw  up  a  reply.  He  ac- 
cordingly entered  the  lists  on  the  mathematical  part 
of  the  controversy,  and  left  the  philosophical  part 
of  it  to  Dr.  Clarke,  who  was  a  full  match  for  the 
jrerman  philosopher.  The  correspondence  which 
hus  took  place  was  carefully  perused  by  the  prin- 
cess, and  from  the  estimation  in  which  Sir  Isaac 
Continued  to  be  held,  we  may  infer  that  the  views  of 
,he  English  philosopher  were  not  very  remote  from 
ler  own. 

When  Sir  Isaac  was  one  day  conversing  with  her 
•oyal  highness  on  some  points  of  ancient  history, 
le  was  led  to  mention  to  her,  and  to  explain,  a  new 
system  of  chronology  which  he  composed  during  his 
residence  at  Cambridge,  where  he  was  in  the  habit, 
as  he  himself  expresses  it,  "of  refreshing  himself 
with  history  and  chronology  when  he  was  weary 
with  other  studies."  The  princess  was  so  much 
pleased  with  his  ingenious  system,  that  she  subse- 
quently, in  the  year  1718,  sent  a  message  by  the  Abb6 
Conti  to  Sir  Isaac,  requesting  him  to  speak  with  her, 
and  she,  on  this  occasion,  requested  a  copy  of  the 
interesting  work  which  contained  his  system  of  chro- 
nology. Sir  Isaac  informed  her  that  it  existed  merely 
in  separate  papers,  which  were  not  only  in  a  state 
of  confusion,  but  which  contained  a  very  imperfect 
view  of  the  subject,  and  he  promised,  in  a  few  days, 
to  draw  up  an  abstract  of  it  for  her  own  private  use, 
and  on  the  condition  that  it  should  not  be  communi- 
cated to  any  other  person.  Some  time  after  the 


236  sm  ISAAC  NEWTON. 

princess  received  the  manuscript,  she  requested  that 
the  Abbe*  Conti  might  be  allowed  to  have  a  copy  of 
it.  Sir  Isaac  granted  this  request,  and  the  Abbe  was 
informed  that  he  received  a  copy  of  the  manuscript 
with  Sir  Isaac's  leave,  and  at  the  princess's  request, 
and  that  it  was  to  be  kept  secret.*  The  manuscript 
which  was  thus  rashly  put  into  the  hands  of  a 
foreigner  was  entitled  "  A  Short  Chronicle  from  the 
First  Memory  of  Things  in  Europe  to  the  Conquest 
of  Persia  by  Alexander  the  Great."  It  consists  of 
about  twenty-four  quarto  printed  pages,f  with  an 
introduction  of  four  pages,  in  which  Sir  Isaac  states 
that  he  "  does  not  pretend  to  be  exact  to  a  year,  that 
there  may  be  errors  of  five  or  ten  years,  and  some- 
times twenty,  but  not  much  above." 

The  Abbe  Conti  kept  his  promise  of  secrecy  during 
his  residence  in  England,  but  he  no  sooner  reached 
Paris  than  he  communicated  it  to  M.  Freret,  a 
learned  antiquarian,  who  not  only  translated  it,  but 
drew  up  observations  upon  it  for  the  purpose  of  re- 
futing some  of  its  principal  results.  Sir  Isaac  was 
unacquainted  with  this  transaction  till  he  was  in- 
formed of  it  by  the  French  bookseller,  M.  Cavalier, 
who  requested  his  leave  to  publish  it,  and  charged 
one  of  his  friends  in  London  to  procure  Sir  Isaac's 
answer,  which  was  as  follows : — 

"  I  remember  that  I  wrote  a  Chronological  index 
for  a  particular  friend,  on  condition  that  it  should  not 
be  communicated.  As  I  have  not  seen  the  manu- 
script which  you  have  under  my  name,  I  know  not 
whether  it  be  the  same.  That  which  I  wrote  was 
not  at  all  done  with  design  to  publish  it.  I  intend 
not  to  meddle  with  that  which  hath  been  given  you 

*  This  anecdote  concerning  the  Chronological  manuscript  is  not  cor- 
rectly given  in  the  Biographia  Britannica,  and  in  some  of  the  other  lives 
of  Newton.  I  have  followed  implicitly  Newton's  own  account  of  it  in 
the  Phil.  Trans.  1725,  vol.  xxxiii.  No.  389,  p.  315. 

t  M.  Biot  has  supposed  that  this  abstract  was  an  imperfect  edition  of 
Newton's  work  on  Chronology. 


CHRONOLOGY.  237 

T  my  name,  nor  to  give  any  consent  to  the  pub- 
ishing  of  it. — I  am  your  very  humble  servant, 

"ISAAC  NEWTON. 
"London,  May  21th,  1725,  0.  S." 

Before  this  letter  was  written,  viz.  on  the  21st 
May,  the  bookseller  had  received  the  royal  privilege 
"or  printing  the  work ;  and  when  it  was  completed, 
le  sent  a  copy  in  a  present  to  Sir  Isaac,  who  received 
t  on  the  llth  November,  1725.  It  was  entitled, 
Abrege  de  Chronologie  de  M.  Le  Chevalier  Newton, 
fait  par  lui-meme,  et  traduit  sur  le  manuscript  Anglais, 
tod  was  accompanied  with  observations  by  M.  Fre- 
ret,*  the  object  of  which  was  to  refute  the  leading 
points  of  the  system.f  An  advertisement  was  pre- 
ixed  to  it,  in  which  the  bookseller  defends  himself 
"or  printing  it  without  the  author's  leave,  on  the 
round  that  he  had  written  three  letters  to  obtain 
)ermission,  and  had  declared  that  he  would  take  Sir 
isaac's  silence  for  consent.  When  Sir  Isaac  received 
,his  work,  he  drew  up  a  paper  entitled,  Remarks  on 
'he  Observations  made  on  a  Chronological  Index  of  Sir 
Isaac  Newton,  translated  into  French  by  the  Observator, 
md  published  at  Paris,  which  was  printed  in  the  Phi- 
losophical Transactions  for  1725.J  In  this  paper  Sir 
[saac  gives  a  history  of  the  transaction,- — charges 
,he  Abbe  Conti  with  a  breach  of  promise,  and  blames 
;he  publisher  for  having  asked  his  leave  to  print  the 
;ranslation  without  sending  him  a  copy  for  his  peru- 
sal, without  acquainting  him  with  the  name  of  the 
translator,  and  without  announcing  his  intention  of 
printing  along  with  it  a  refutation  of  the  original. 

Father  Souciet  was  supposed  by  Halley  and  others  to  have  been  the 
authorof  these  observations,  but  there  is  no  doubt  that  they  were  written 
by  M.  Freret. 

•f  It  is  stated  in  the  Biogr.  Britannica,  Art.  Newton,  that  the  copy  of 
the  French  translation  was  not  accompanied  with  the  refutation.  Though 
the  reverse  of  this  is  not  distinctly  stated  by  Sir  Isaac  himself,  yet  it 
may  be  inferred  from  his  observations. 

%  Vol.  xxxiii.  No.  389,  p.  315. 


238  SIR    ISAAC  NEWTON. 

The  observations  made  by  the  translator  against  the 
conclusions  deduced  by  the  author  were  founded  on 
an  imperfect  knowledge  of  Sir  Isaac's  system ;  and 
they  are  so  specious,  that  Halley  himself  confesses 
that  he  was  at  first  prejudiced  in  favour  of  the  obser- 
vations, taking  the  calculations  for  granted,  and  not 
having  seen  Sir  Isaac's  work. 

To  all  the  observations  of  M.  Freret  Sir  Isaac  re- 
turned a  triumphant  answer.  This  presumptuous 
antiquary  had  ventured  to  state  at  the  end  of  his 
observations,  "  that  he  believed  he  had  stated  enough 
concerning  the  epochs  of  the  Argonauts,  and  the 
length  of  generations,  to  make  people  cautious  about 
the  rest;  for  these  are  the  two  foundations  of  all  this 
new  system  of  chronology."  He  founds  his  argu- 
ments against  the  epochs  of  the  Argonauts,  as  fixed 
by  our  author,  on  the  supposition  that  Sir  Isaac 
places  the  vernal  equinox  at  the  time  of  the  Argo- 
nautic  expedition  in  the  middle  of  the  sign  of  Ariesj 
whereas  Sir  Isaac  places  it  in  the  middle  of  the  con- 
stellation,— a  point  corresponding  with  the  middle  of 
the  back  of  Aries,  or  8°  from  the  first  star  of  Aries. 
This  position  of  the  colure  is  assigned  on  the  author- 
ity of  Eudoxus,  as  given  by  Hipparchus,  who  says 
that  the  colure  passed  over  the  back  of  Aries.  Set- 
ting out  with  this  mistake,  M.  Freret  concludes  that 
the  Argonautic  expedition  took  place  532  years 
earlier  than  Sir  Isaac  made  it.  His  second  objection 
to  the  new  system  relates  to  the  length  of  genera 
tipns,  which  he  says  is  made  only  18  or  20  years. 
Sir  Isaac,  on  the  contrary,  reckons  a  generation  at 
33  years,  or  3  generations  at  100 ;  and  it  was  the 
lengths  of  the  reigns  of  kings  that  he  made  18  or  20 
years.  This  deduction  he  founds  on  the  reigns  of 
64  French  kings.  Now,  the  ancient  Greeks  and 
Egyptians  reckoned  the  length  of  a  reign  equal  to 
that  of  a  generation ;  and  it  was  by  correcting  this 
mistake,  and  adopting  a  measure  founded  on  fact, 
that  Sir  Isaac  placed  the  Argonautic  expedition  forty- 


CHRONOLOGY.  239 

bur  years  after  the^death  of  Solomon,  and  fixed  some 
>f  the  other  points'  of  his  system. 

This  answer  of  Sir  Isaac's  to  the  objections  of 
<Yeret  called  into  the  field  a  fresh  antagonist,  Father 
Souciet,  who  published  five  dissertations  on  the  new 
chronology.  These  dissertations  were  written  in 

tone  highly  reprehensible ;  and  the  friends  of  Sir 
'saac,  being  apprehensive  that  the  manner  in  which 
lis  system  was  attacked  would  affect  him  more  than 
he  arguments  themselves,  prevailed  upon  a  friend  to 
raw  up  an  abstract  of  Souciet's  objections,  stripped 
>f  the  "  extraordinary  ornaments  with  which  they 
*vere  clothed."  The  perusal  of  these  objections  had 
10  other  effect  upon  him  than  to  convince  him  of 
;he  ignorance  of  their  author ;  and  he  was  induced 
:o  read  the  entire  work,  which  produced  no  change 
n  his  opinion. 

In  consequence  of  these  discussions,  Sir  Isaac 
was  prevailed  upon  to  prepare  his  larger  work  for 
;he  press. v  He  had  nearly  completed  it  at  the  time 
)f  his  death,  and  it  was  published  in  1728,  under  the 
itleof  The  Chronology  of  Ancient  Kingdoms  amended, 
o  which  is  prefixed  a  short  Chronicle,  from  the  first 
memory  of  Things  in  Europe  to  the  Conquest  of  Per- 
ia  by  Alexander  the  Great.  It  was  dedicated  to  the 
jueen  by  Mr.  Conduit,  and  consists  of  six  chapters : 

On  the  Chronology  of  the  Greeks  ;*  2.  Of  the 
Empire  of  Egypt ;  3.  Of  the  Assyrian  Empire ;  4. 
)f  the  two  contemporary  Empires  of  the  Baby- 
onians  and  Medes ;  5.  A  Description  of  the  Temple 
)f  Solomon;  6.  Of  the  Empire  of  the  Persians. 
The  sixth  chapter  was  not  copied  out  with  the  other 
ive,  which  makes  it  doubtful  whether  or  not  it  was 
ntended  for  publication ;  but  as  it  was  found  among 
lis  papers,  and  appeared  to  be  a  continuation  of  the 

'  According  to  Whiston,  Sir  Isaac  wrote  out  eighteen  copies  of  thta 
hapter  with  'his  own  hand,  differing  little  from  one  another  —  Whi* 
on'vLife,  p.  39. 


240  SIR  ISAAC   NEWTON. 

same  work,  it  was  thought  right  to  add  it  to  the 
other  five  chapters.* 

After  the  death  of  Newton,  Dr.  Halley,  who  had 
not  yet  seen  the  larger  work,  felt  himself  called  upon, 
both  as  astronomer-royal  and  as  the  friend  of  the 
author,  to  reply  to  the  first  and  last  dissertations  of 
Father  Souciet,  which  were  chiefly  astronomical; 
and  in  two  papers  printed  in  the  Philosophical  Trans- 
actions for  1727,f  he  has  done  this  in  a  most  con- 
vincing and  learned  argument. 

\  Among  the  supporters  of  the  views  of  Newton,  . 
we  may  enumerate  Dr.  Reid,  Nauze,  and  some  other- 
writers  ;  and  among  its  opponents,  M.  Freret,  who 
left  behind  him  a  posthumous  work  on  the  subject, 
M.  Fourmond,  Mr.  A.  Bedford,  Dr.  Shuckford,  Dr. 
Middleton,  Whiston,  and  the  late  M.  Delambre.  The 
object  of  M.  Fourmond  is  to  show  the  uncertainty 
of  the  astronomical  argument,  arising  on  the  one 
hand  from  the  vague  account  of  the  ancient  sphere 
as  given  by  Hipparchus ;  and,  on  the  other,  from  the 
extreme  rudeness  of  ancient  astronomical  observa- 
tions. Delambre  has  taken  a  similar  view  of  the 
subject :  he  regards  the  observations  of  ancient 
astronomers  as  too  incorrect  to  form  the  basis  of  a 
system  of  chronology ;  and  he  maintains,  that  if  we 
admit  the  accuracy  of  the  details  in  the  sphere  of 
Eudoxus,  and  suppose  them  all  to  belong  to  the 
.same  epoch,  all  the  stars  which  it  contains  ought  at 
that  epoch  to  be  found  in  the  place  where  they  are 
marked,  and  we  might  thence  verify  the  accuracy, 
and  ascertain  the  state  of  the  observations.  It  fol- 
lows, however,  from  such  an  examination,  that  the 

*  This  work  is  the  first  article  in  the  fifth  volume  of  Dr.  Horsley's 
edition  of  Newton's  works.  The  next  article  in  the  volume  is  entitled, 
"  A  Short  Chronicle  from  a  MS.,  the  property  of  the  Reverend  Dr. 
Ekins,  Dean  of  Carlisle;"  which  is  nothing  more  than  the  abstract  of 
the  Chronology  already  printed  in  the  same  volume.  We  cannot  even 
conjecture  the  reasons  for  publishing  it,  especially  as  it  is  less  perfect 
than  the  abstract,  two  or  three  dates  being  wanting. 

t  See  vol.  xxxiv.  p.  205,  and  vol.  xxxv.  p.  296 


CHRONOLOGY.  241 

;  sphere  would  indicate  almost  as  many  different 
.epochs  as  it  contains  stars.  Some  of  them  even 
had  not,  in  the  time  of  Eudoxus,  arrived  at  the  po- 
sition which  had  been  for  a  long  time  attributed  to 
them,  and  will  not  even  reach  it  for  three  hundred 
years  to  come,  and  on  this  account  he  considers  it 
impossible  to  deduce  any  chronological  conclusions 
from  such  a  rude  mass  of  errors. 

But  however  well-founded  these  observations  may 

,  we  agree  in  opinion  with  M.  Daunou,*  "that 
they  are  not  sufficient  to  establish  a  new  system, 
and  we  must  regard  the  system  of  Newton  as  a 
great  fact  in  the  history  of  chronological  science, 
and  as  confirming  the  observation  of  Varro,  that  the 
stage  of  history  does  not  commence  till  the  first 
Olympiad." 

Among  the  chronological  writings  of  Sir  Isaac 
Newton  we  must  enumerate  his  letter  to  a  person 
of  distinction  who  had  desired  his  opinion  of  the  learned 
Bishop  Lloyd^s  hypothesis  concerning  the  form  of  the 
most  ancient  year.  This  hypothesis  was  sent  by  the 
Bishop  of  Worcester  to  Dr.  Prideaux.  Sir  Isaac 
remarks,  that  it  is  filled  with  many  excellent  obser- 
vations on  the  ancient  year ;  but  he  does  not  "  find 
"t  proved  that  any  ancient  nations  used  a  year  of 
twelve  months  and  360  days  without  correcting  it 

m  time  to  time  by  the  luminaries,  to  make  the 
months  keep  to  the  course  of  the  moon,  and  the  year 
to  the  course  of  the  sun,  and  returns  of  the  seasons 
and  fruits  of  the  earth."  After  examining  the  years 
of  all  the  nations  of  antiquity,  he  concludes, "  that  no 
other  years  are  to  be  met  with  among  the  ancients 
3ut  such  as  were  either  luni-solar,  or  solar  or  lunar, 
or  the  calendars  of  these  years."  A  practical  year, 
tie  adds,  of  360  days  is  none  of  these.  The  begin- 
ning of  such  a  year  would  have  run  round  the  four 

*  See  an  excellent  view  of  this  chronological  controversy  in  an  able 
note  by  M.  Daunou,  attached  to  Biot's  Life  of  Newton  in  the  Biog.  Uni 
versellet  tom-  xxxi.  p.  180 

A. 


242  SIR   ISAAC   NEWTON. 

seasons  in  seventy  years,  and  such  a  notable  revolu- 
tion would  have  been  mentioned  in  history,  and  is 
not  to  be  asserted  without  proving  it.* 


CHAPTER  XVI. 

Theological  Studies  of  Sir  Isaac— Their  Importance  to  Christianity— 
Motives  to  which  they  have  been  ascribed— Opinions  of  Biot  and  La-  ' 
place  considered — His  Theological  Researches  begun  before  his  sup* 
posed  Mental  Illness— The  Date  of  these  Works  fixed— Letters  to  Locke 
— Account  of  his  Observations  on  Prophecy- -His  Historical  Account 
of  two  notable  Corruptions  of  Scripture — His  Lexicon  Propheticum — 
His  Four  Letters  to  Dr.  Bentley — Origin  of  Newton's  Theological 
Studies— Analogy  between  the  Book  of  Nature  and  that  of  Revelation 

THE  history  of  the  theological  studies  of  Sir  Isaac 
Newton  will  ever  be  regarded  as  one  of  the  most 
interesting  portions  of  his  life.  That  he  who  among 
all  the  individuals  of  his  species  possessed  the  high- 
est intellectual  powers  was  not  only  a  learned  and , 
profound  divine,  but  a  firm  believer  in  the  great  doc- 
trines of  religion,  is  one  of  the  proudest  triumphs 
of  the  Christian  faith.  Had  he  distinguished  him- 
self only  by  an  external  respect  for  the  offices  and 
duties  of  religion ;  and  had  he  left  merely  in  his  last 
words  an  acknowledgment  of  his  faith,  his  piety 
would  have  been  regarded  as  a  prudent  submission 
to  popular  feeling,  and  his  last  aspirations  would 
have  been  ascribed  to  the  decay  or  to  the  extinction 
of  his  transcendent  powers.  But  he  had  been  a 
Christian  from  his  youth,  and  though  never  intended 
for  the  church,  yet  he  interchanged  the  study  of  the 
Scriptures  with  that  of  the  laws  of  the  material 
universe ;  and  from  the  examination  of  the  works 
of  the  Supreme  Creator-  he  found  it  to  be  no  abrupt 

*  This  letter  is  published  without  any  date  in  the  Gentleman's  Maga- 
zine for  1755^vol.  xxv.  p.  3.   It  bears  internal  evidence  of  being  genuine 


THEOLOGICAL   STUDIES.  243 

transition  to  investigate  the  revelation  of  his  will, 
fand  to  contemplate  the  immortal  destinies  of  man- 
[kind. 

But  when  the  religious  habits  of  Sir  Isaac  Newton 
[could  not  be  ascribed  to  an  ambiti6n  of  popularity, 
to  the  influence  of  weak  health,  or  to  the  force  of 
[professional  impulse,  it  became  necessary  for  the 
apostles  of  infidelity  to  refer  it  to  some  extraordi- 
nary cause.  His  supposed  insanity  was  therefore 
eagerly  seized  upon  by  some  as  affording  a  plausible 
origin  for  his  religious  principles ;  while  others, 
without  any  view  of  supporting  the  cause  of  skep- 
ticism, ascribed  his  theological  researches  to  the 
habits  of  the  age  in  which  he  lived,  and  to  a  desire 
of  promoting  political  liberty,  by  turning  against  the 
abetters  of  despotism  those  powerful  weapons  which 
the  Scriptures  supplied.  The  anxiety  evinced  by 
M.  de  Laplace  to  refer  his  religious  writings  to  a 
late  period  of  his  life  seems  to  have  been  felt  also 
by  M.  Biot,  who  has  gone  so  far  as  to  fix  the  very 
date  of  one  of  his  most  important  works,  and  thus 
to  establish  the  suspicions  of  his  colleague. 

'  From  the  nature  of  the  subject,"*  says  he, "  and 
from  certain  indications  which  Newton  seems  to 
give  at  the  beginning  of  his  dissertation,  we  may 
conjecture  with  probability  that  he  composed  it  at 
the  time  when  the  errors  of  Whiston,  and  a  work 
of  Dr.  Clarke  on  the  same  subject,  drew  upon  them 
the  attacks  of  all  the  theologians  of  England,  which 
would  place  the  date  between  the  years  1712  and 
1719.  It  would  then  be  truly  a  prodigy  to  remark, 
that  a  man  of  from  seventy-two  to  seventy-five 
years  of  age  was  able  to  compose,  rapidly,  as  he 
leads  us  to  believe,  so  extensive  a  piece  of  sacred 
criticism,  of  literary  history,  and  even  of  bibliogra- 
phy, where  aa  erudition  the  most  vast,  the  most 

*  His  Historical  Account  of  two  notable  Corruptions  of  tiu  Scrip- 
tures. 50  pp  quarto. 


SIR    ISAAC   NEWTON. 


varied,  and  the  most  ready  always  supports  an  argu- 
ment well  arranged  and  powerfully  combined.  * 
At  this  epoch  of  the  life  of  Newton  the  reading  ol 
religious  books  had  become  one  of  his  most  habitual 
occupations,  and  after  he  had  performed  the  duties 
of  his  office,  they  formed,  along  with  the  conversa- 
tion of  his  friends,  his  principal  amusement.  He 
had  then  almost  ceased  to  care  for  the  sciences,  and, 
IN  we  have  already  remarked,  since  the  fatal  epoch 
of  1693,  he  gave  to  the  world  only  three  really  new 
scientific  productions." 

Notwithstanding  the  prodigy  which  it  involves,  M. 
Biot  has  adopted  1712-1719  as  the  date  of  this  criti- 
cal dissertation  ;  —  it  is  regarded  as  the  composition 
of  a  man  of  seventy-two  or  seventy-five  ;  —  the  read- 
ing of  religious  works  is  stated  to  have  become  one  of 
his  most  habitual  occupations,  and  such  reading  is 
said  to  have  been  one  of  his  principal  amusements  ; 
and  all  this  is  associated  with  "  the  fatal  epoch  of 
1693,"  as  if  his  illness  at  that  time  had  been  the 
cause  of  his  abandoning  science  and  betaking  him- 
self to  theology.  Carrying  on  the  same  views,  M. 
Biot  asks,  in  reference  to  Sir  Isaac's  work  on  Pro- 
phecy, "  How  a  mind  of  the  character  and  force  of 
Newton's,  so  habituated  to  the  severity  of  mathe 
matical  considerations,  so  exercised  in  the  observa- 
tion of  real  phenomena,  and  so  well  aware  of  the 
conditions  by  which  truth  is  to  be  discovered,  could 
put  together  such  a  number  of  conjectures  without 
noticing  the  extreme  improbability  of  his  interpreta- 
tions from  the  infinite  number  of  arbitrary  postulates 
on  which  he  has  founded  them  ?"  We  would  apply 
the  same  question  to  the  reasoning  by  which  M.  Biot 
fixes  the  date  of  the  critical  dissertation  ;  and  we 
would  ask  how  so  eminent  a  philosopher  could  haz- 
ard such  frivolous  conjectures  upon  a  subject  on 
which  he  had  not  a  single  fact  to  guide  his  inquiries. 
The  obvious  tendency,  though  not  the  design,  of  the 
conclusion  at  which  he  arrives  is  injurious  to  the 


LETTERS   TO   LOCKE.  245 

memory  of  Newton,  as  well  as  to  the  interests  of 
religion;  and  these  considerations  might  have 
checked  the  temerity  of  speculation,  even  if  it  had 
been  founded  on  better  data.  The  Newtonian  inter- 
pretation of  the  Prophecies,  and  especially  that  part 
which  M.  Biot  characterizes  as  unhappily  stamped 
with  the  spirit  of  prejudice,  has  been  adopted  by  men 
of  the  soundest  and  most  unprejudiced  minds;  and 
in  addition  to  the  moral  and  historical  evidence  by 
which  it  is  supported,  it  may  yet  be  exhibited  in  all 
the  fulness  of  demonstration.  But  the  speculation 
of  Biot  respecting  the  date  of  Newton's  theological 
works  was  never  maintained  by  any  other  person 
than  himself,  and  is  capable  of  being  disproved  by 
the  most  incontrovertible  evidence. 

We  have  already  seen,  in  the  extract  from  Mr. 
Pryme's  manuscript,  that  previous  to  1692,  when  a 
shade  is  supposed  to  have  passed  over  his  gifted 
mind,  Newton  was  well  known  by  the  appellation 
of  an  "  excellent  divine," — a  character  which  could 
not  have  been  acquired  without  the  devotion  of  many 
years  to  theological  researches ;  but,  important  as 
this  argument  would  have  been,  we  are  fortunately 
not  left  to  so  general  a  defence.  The  correspond- 
ence of  Newton  with  Locke,  recently  published  by 
Lord  King,  places  it  beyond  a  doubt  that  he  had  be- 
gun his  researches  respecting  the  Prophecies  before 
the  year  1691, — before  the  forty-ninth  year  of  his 
age,  and  before  the  "fatal  epoch  of  1693."  The 
following  letter  shows  that  he  had  previously  dis- 
cussed this  subject  with  his  friend  : — 

«  SIR,  Cambridge,  Feb.  7,  1690-1. 

"I  am  sorry  your  journey  proved  to  so  little  pur- 
pose, though  it  delivered  you  from  the  trouble  of  the 
company  the  day  after.  You  have  obliged  me  by 
mentioning  me  to  my  friends  at  London,  and  I  must 
thank  both  you  and  my  Lady  Masham  for  your 
civilities  at  Gates,  and  for  not  thinking  that  I  made 

A  * 


246  «IR   ISAAC   NEWTON. 

a  long  stay  there.  J  hope  we  shall  meet  again  in 
due  time,  and  then  I  should  be  glad  to  have  your 
judgment  upon  some  of  my  mystical  fancies.  The 
Son  of  Man,  Dan.  vii.  I  take  to  be  the  same  with  the 
Word  of  God  upon  the  White  Horse  in  Heaven, 
Apoc.  xii.,  for  both  are  to  rule  the  nations  with  a  rod 
of  iron ;  but  whence  are  you  certain  that  the  Ancient 
of  Days  is  Christ  ?  Does  Christ  anywhere  sit  upon 
the  throne  1  If  Sir  Francis  Masham  be  at  Gates, 
present,  I  pray,  my  service  to  him,  with  his  lady, 
Mrs.  Cudworth,  and  Mrs.  Masham.  Dr.  Covel  is 
not  in  Cambridge. — I  am  your  affectionate  and " 
humble  servant,  "  Is.  NEWTON 

'Know  you  the  meaning  of  Dan.  x.  21.  There 
is  none  that  holdeth  with  me  in  these  things  but 
Mich,  the  prince." 

Having  thus  determined  the  date  of  those  investi- 
gations which  constitute  his  observations  on  the  pro- 
phecies of  holy  writ,  particularly  the  prophecies  of 
Daniel  and  the  Apocalypse,  we  shall  proceed  to  fix 
the  latest  date  of  his  historical  account  of  two  notable 
corruptions  of  the  Scripture,  in  a  letter  to  a  friend. 

This  work  seems  to  have  been  a  very  early  pro- 
duction of  our  author.  It  was  written  in  the  form 
of  a  letter  to  Mr.  Locke,  and  at  that  time  Sir  Isaac 
seems  to  have  been  anxious  for  its  publication. 
Afraid,  however,  of  being  again  led  into  a  contro- 
versy, and  dreading  the  intolerance  to  which  he 
might  be  exposed,  he  requested  Mr.  Locke,  who 
was  at  that  time  meditating  a  voyage  to  Holland, 
to  get  it  translated  into  French,  and  published  on 
the  Continent.  Having  abandoned  his  design  of 
visiting  Holland,  Locke  transmitted  the  manuscript, 
without  Newton's  name,  to  his  learned  friend  M.  Le 
Clerc,  in  Holland ;  and  it  appears,  from  a  letter  of 
Le  Clerc's  to  Locke,  that  he  must  have  received  it 
before  the  llth  April,  1691.  M.  Le  Clerc  delayed 


LETTERS   TO   LOCKE.  247 

for  a  long  time  to  take  any  steps  regarding  its  pub- 
lication ;  but  in  a  letter  dated  January  20th,  1692,  he 
announced  to  Locjte  his  intention  of  publishing  the 
tract  in  Latin.  When  this  plan  was  communicated 
to  Sir  Isaac,  he  became  alarmed  at  the  risk  of  de- 
tection, and  resolved  to  stop  the  publication  of  his 
manuscript.  This  resolution  was  intimated  to  Mr. 
Locke  in  the  following  letter : 

"  SIR,  Cambridge,  Feb.  Uth,  1691-2. 

"  Your  former  letters  came  not  to  my  hand,  but 
this  I  have.  I  was  of  opinion  my  papers  had  lain 
still,  and  am  sorry  to  hear  there  is  news  about  them. 
Let  me  entreat  you  to  stop  their  translation  and  im- 
pression so  soon  as  you  can ;  for  I  design  to  suppress 
them.  If  your  friend  hath  been  at  any  pains  and 
charge,  I  will  repay  it,  and  gratify  him.  I  am  very 
glad  my  Lord  Monmouth  is  till  my  friend,  but  intend 
not  to  give  his  lordship  and  you  any  farther  trouble. 
My  inclinations  are  to  sit  still.  I  am  to  beg  his 
lordship's  pardon  for  pressing  into  his  company  the 
last  time  I  saw  him.  I  had  not  done  it,  but  that  Mr. 
Paulin  pressed  me  into  the  room.  Miracles,  of 
good  credit,  continued  in  the  church  for  about  two 
or  three  hundred  years.  Gregorius  Thaumaturgus 
had  his  name  from  thence,  and  was  one  of  the  latest 
who  was  eminent  for  that  gift ;  but  of  their  number 
and  frequency  I  am  not  able  to  give  you  a  just  ac- 
count. The  history  of  those  ages  is  very  imperfect. 
Mr.  Paulin  told  me  you  had  writ  for  some  of  Mr 
Boyle's  red  earth,  and  by  that  I  knew  you  had  the 
receipt. — Your  most  affectionate  and  humble  servant, 

"  Is.  NEWTON." 

Hence  we  see  that  this  celebrated  treatise,  which 
Biot  alleges  to  have  been  written  between  1712  and 
1719,  was  actually  in  the  hands  of  Le  Clerc  in  Hol- 
land previous  to  the  llth  April,  1691,  and  conse- 
quently previous  to  the  time  of  the  supposed  insanity 


248  SIR   ISAAC   NEWTON. 

of  its  author.  Mr.  Locke  lost  no  time  in  obeying  the 
request  of  his  friend.  Le  Clerc  instantly  stopped  the 
publication  of  the  letter,  and,  as  he  had  never  learned 
the  name  of  the  author,  he  deposited  the  manuscript, 
which  was  in  the  handwriting  of  Mr.  Locke,  in  the 
library  of  the  Remonstrants,  where  it  was  afterward 
found,  and  was  published  at  London  in  1754,  under 
the  title  of  Two  letters  from  Sir  Isaac  Newton  to  M. 
Le  Clerc, — a  form  which  had  never  been  given  to  it 
by  its  author.  The  copy  thus  published  was  a  very 
imperfect  one,  wanting  both  the  beginning*  and  the 
end,  and  erroneous  in  many  places ;  but  Dr.  Horsley 
has  published  a  genuine  edition,  which  has  the  form 
of  a  single  letter  to  a  friend,  and  was  copied  from  a 
manuscript  in  Sir  Isaac  Newton's  handwriting,  in  the 
possession  of  the  Rev.  Dr.  Ekins,  Dean  of  Carlisle. 

Having  thus  determined  as  accurately  as  possible 
the  dates  of  the  principal  theological  writings  of  Sir 
Isaac,  we  shall  now  proceed  to  give  some  account 
of  their  contents. 

The  Observations  on  the  Prophecies  of  Daniel  and 
the  Apocalypse  of  St.  John  were  published  in  London 
in  1733,  in  one  volume  4to.  The  work  is  divided 
into  two  parts,  the  first  of  which  treats  of  the  Pro- 
phecies of  Daniel,  and  the  second  of  the  Apocalypse 
of  St.  John.  It  begins  with  an  account  of  the  dif- 
ferent books  which  compose  the  Old  Testament ;  and 
as  the  author  considers  Daniel  to  be  the  most  dis- 
tinct in  the  order  of  time,  and  the  easiest  to  be  un- 
derstood, he  makes  him  the  key  to  all  the  prophetic 
books  in  those  matters  which  relate  to  the  "last  time." 
He  next  considers  the  figurative  language  of  the 
prophets,  which  he  regards  as  taken  "  from  the 
analogy  between  the  world  natural  and  an  empire 
or  kingdom  considered  as  a  world  politic ;"  the  hea- 
vens and  the  things  therein  representing  thrones  and 
dynasties;  the  earth,  with  the  things  therein,  the 

*  The  editor  supplied  the  beginning  down  to  the  13th  page,  where  he 
mentions  in  a  note  that  "thus  far  is  not  Sir  Isaac's." 


OBSERVATIONS  ON  PROPHECY.       249 

"erior  people ;  and  the  lowest  parts  of  the  earth 
the  most  miserable  of  the  people.    The  sun  is  put 
for  the  whole  race  of  kings,  the  moon  for  the  body 
of  the  common  people,  and  the  stars  for  subordinate 
:  princes  and  rulers.     In  the  earth,  the  dry  land  and 
the  waters  are  put  for  the  people  of  several  nations. 
j  Animals  and  vegetables  are  also  put  for  the  people 
i  of  several  regions.    When  a  beast  or  man  is  put  for 
f  a  kingdom,  his  parts  and  qualities  are  put  for  the 
£  analogous  parts  and  qualities  of  the  kingdom ;  and 
i when  a  man  is  taken  in  a  mystical  sense,  his  quali- 
i  ties  are  often  signified  by  his  actions,  and  by  the 
circumstances  and  things  about  him.     In  applying 
?  these  principles  he  begins  with  the  vision  of  the 
'image  composed  of   four  different  metals.    This 
i  image  he  considers  as  representing  a  body  of  four 
great  nations  which  should  reign  in  succession  over 
the  earth,  viz.  the  people  of  Babylonia,  the  Persians, 
the  Greeks,  and  the  Romans ;  while  the  stone  cut  out 
without  hands  is  a  new  kingdom  which  should  arise 
I  after  the  four,  conquer  all  those  nations,  become  very 
great,  and  endure  to  the  end  of  time. 

The  vision  of  the  four  beasts  is  the  prophecy  of  the 
four  empires  repeated,  with  several  new  additions. 
1  The  lion  with  eagles'  wings  was  the  kingdom  of 
Babylon  and  Media,  which  overthrew  the  Assyrian 
power.    The  beast  like  a  bear  was  the  Persian  em- 
pire, and  its  three  ribs  were  the  kingdoms  of  Sardis, 
|  Babylon,  and  Egypt.    The  third  beast,  like  a  leopard, 
I  was  the  Greek  empire,  and  its  four  heads  and  four 
1  wings  were  the  kingdoms  of  Cassander,  Lysimachus, 
Ptolemy,  and  Seleucus.     The  fourth  beast,  with  its 
great  iron  teeth,  was  the  Roman  empire,  and  its  ten 
horns  were  the  ten  kingdoms  into  which  it  was 
broken  in  the  reign  of  Theodosius  the  Great. 

In  the  fifth  chapter  Sir  Isaac  treats  of  the  king- 
doms represented  by  the  feet  of  the  image  composed 
of  iron  and  clay  which  did  not  stick  to  one  another, 
and  which  were  of  different  strength.  These  were 


250  SIR   ISAAC  NEWTON. 

the  Gothic  tribes  called  Ostrogoths,  Visigoths,  Van- 
dais,  Gepidae,  Lombards,  Burgundians,  Alans,  &c. ; 
all  of  whom  had  the  same  manners  and  customs, 
and  spoke  the  same  language,  and  who,  about  the 
year  416  A.  C.  were  all  quietly  settled  in  several 
kingdoms  within  the  empire,  not  only  by  conquest, 
but  by  grants  of  emperor. 

In  the  sixth  chapter  he  treats  of  the  ten  kingdoms 
represented  by  the  ten  horns'of  the  fourth  beast,  into 
which  the  western  empire  became  divided  about  the 
time  when  Rome  was  besieged  and  taken  by  the 
Goths.  These  kingdoms  were, 

1.  The  kingdom  of  the  Vandals  and  Alans  in  Spain 
and  Africa. 

2.  The  kingdom  of  Suevians  in  Spain. 

3.  The  kingdom  of  the  Visigoths. 

4.  The  kingdom  of  the  Alans  in  Gaul. 

5.  The  kingdom  of  the  Burgundians. 

6.  The  kingdom  of  the  Franks. 

7.  The  kingdom  of  the  Britains. 

8.  The  kingdom  of  the  Huns. 

9.  The  kingdom  of  the  Lombards. 
10.  The  kingdom  of  Ravenna. 

Some  of  these  kingdoms  at  length  fell,  and  new 
ones  sprung  up ;  but  whatever  was  their  subsequent 
number,  they  still  retain  the  name  of  the  ten  kings 
from  their  first  number. 

The  eleventh  horn  of  Daniel's  fourth  beast  is  shown 
in  chapter  vii.  to  be  the  Church  of  Rome  in  its  triple 
character  of  a  seer,  a  prophet,  and  a  king ;  and  its 
power  to  change  times  and  laws  is  copiously  illus- 
trated in  chapter  viii. 

In  the  ninth  chapter  our  author  treats  of  the  king- 
dom represented  in  Daniel  by  the  ram  and  he-goat, 
:he  ram  indicating  the  kingdom  of  the  Medes  and 
Persians  from  the  beginning  of  the  four  empires,  and 
the  he-goat  the  kingdom  of  the  Greeks  to  the  end 
of  them. 

The  prophecy  of  the  seventy  weeks,  which  had 


OBSERVATIONS  ON  PROPHECY.       251 


i  hitherto  been  restricted  to  the  first  coming  of  our 
ISaviour,  is  shown  to  be  a  prediction  of  all  the  main 
Jperiods  relating  to  the  coming  of  the  Messiah,  the 
[times  of  his  birth  and  death,  the  time  of  his  rejection 
[by  the  Jews,  the  duration  of  the  Jewish  war  by  which 
[he  caused  the  city  and  sanctuary  to  be  destroyed, 
land  the  time  of  his  second  coming. 

In  the  eleventh  chapter  Sir  Isaac  treats  "rith  great 
[sagacity  and  acuteness  of  the  time  of  our  Saviour's 
[birth  and  passion, — a  subject  which  had  perplexed 
[all  preceding  commentators. 

After  explaining  in  the  twelfth  chapter  the  last 
prophecy  of  Daniel,  namely,  that  of  the  scripture  of 
truth,  which  he  considers  as  a  commentary  on  the 
vision  of  the  ram  and  he-goat,  he  proceeds  in  the 
thirteenth  chapter  to  the  prophecy  of  the  king  who 
did  according  to  his  will,  and  magnified  himself  above 
every  god,  and  honoured  Mahuzzims,  and  regarded 
not  the  desire  of  women.  He  shows  that  the  Greek 
empire,  after  the  division  of  the  Roman  empire  into 
the  Greek  and  Latin  empires,  became  the  king  who 
in  matters  of  religion  did  according  to  his  will,  and 
in  legislation  exalted  and  magnified  himself  above 
every  god. 

In  the  second  part  of  his  work  on  the  Apocalypse 
of  St.  John,  Sir  Isaac  treats,  1st,  Of  the  time  when 
the  prophecy  was  written,  which  he  conceives  to 
have  been  during  John's  exile  in  Patmos,  and  before 
the  epistle  to  the  Hebrews  and  the  epistles  of  Peter 
were  written,  which  in  his  opinion  have  a  reference 
to* the  Apocalypse ;  2dly,  Of  the  scene  of  the  vision, 
and  the  relation  which  the  Apocalypse  has  to  the 
book  of  the  law  of  Moses,  and  to  the  worship  of  God 
in  the  temple ;  and,  Sdly,  Of  the  relation  which  the 
Apocalypse  has  to  the  prophecies  of  Daniel,  and  of 
the  subject  of  the  prophecy  itself. 

Sir  Isaac  regards  the  prophecies  of  the  Old  and 
New  Testaments,  not  as  given  to  gratify  men's  curi 
osities,  by  enabling  them  to  foreknow  things,  but  that 


252  SIR    ISAAC    NEWTON. 

after  they  were  fulfilled,  they  might  be  interpreted 
by  the  event,  and  afford  convincing  arguments  that 
the  woild  is  governed  by  Providence.  He  considers 
that  there  is  so  much  of  this  prophecy  already  ful- 
filled as  to  afford  to  the  diligent  student  sufficient 
instances  of  God's  providence;  and  he  adds,  that 
"  among  the  interpreters  of  the  last  age,  there  is 
scarce  one  of  note  who  hath  not  made  some  discovery 
worth  knowing,  and  thence  it  seems  one  may  gather 
that  God  is  about  opening  these  mysteries.  The 
success  of  others,"  he  continues,  "  put  me  upon  con- 
sidering it,  and  if  I  have  done  any  thing  which  may 
be  useful  to  following  writers,  I  have  my  design." 
,  Such  is  a  brief  abstract  of  this  ingenious  work, 
which  is  characterized  by  great  learning,  and  marked 
with  the  sagacity  of  its  distinguished  author.  The 
same  qualities  of  his  mind  are  equally  conspicuous 
in  his  Historical  Account  of  Two  Notable  Corruptions 
of  Scripture. 

This  celebrated  treatise  relates  to  two  texts  in  the 
Epistles  of  St.  John  and  St.  Paul.  The  first  of  these 
is  in  1  John  v.  7.  "  For  there  are  three  that  bear 
record  in  heaven,  the  Father,  the  Son,  and  the  Holy 
Ghost,  and  these  three  are  one."  This  text  he  con- 
siders as  a  gross  corruption  of  Scripture,  which  had. 
its  origin  among  the  Latins,  who  interpreted  the 
Spirit,  Water,  and  Blood  to  be  the  Father,  Son,  and 
Holy  Ghost,  in  order  to  prove  them  one.  With  the 
same  view  Jerome  inserted  the  Trinity  in  express 
words  in  his  version.  The  Latins  marked  his  varia- 
tions in  the  margins  of  their  books;  and  in  the 
twelfth  and  following  centuries,  when  the  disputa- 
tions of  the  schoolmen  were  at  their  height,  the 
variation  began  to  creep  into  the  text  in  transcribing. 
After  the  invention  of  printing,  it  crept  out  of  the 
Latin  into  the  printed  Greek,  contrary  to  the  author- 
ity of  all  the  Greek  manuscripts  and  ancient  ver- 
sions; and  from  the  Venetian  press  it  went  soon 
after  into  Greece.  After  proving  these  positions 


CORRUPTIONS   OF   SCRIPTURE.  253 

Sir  Isaac  gives  the  following  paraphrase  of  this  re- 
•'*  markable  passage,  which  is  given  in  italics. 

"  Who  is  he  that  overcometh  the  world,  but  he  that 
$  lelieveth  that  Jesus  is  the  Son  of  God,  that  Son  spoken 
I  of  in  the  Psalms,  where  he  saith,  '  thou  art  my  Son ; 
I  this  day  have  1  begotten  thee.'     This  is  he  that,  after 
I  the  Jews  had  long  expected  him,  came,  first  in  a  mor- 
I  tal  body,  by  baptism  of  water,  and  then  in  an  immor- 
I  tal  one,  by  shedding  his  blood  upon  the  cross  and 
I  rising  again  from  the  dead ;  not  by  water  only,  but 
\  by  water  and  blood ;  being  the  Son  of  God,  as  well 
by  his  resurrection  from  the  dead  (Acts  xiii.  33),  as 
I  by  his  supernatural  birth  of  the  virgin  (Luke  i.  35). 
j  And  it  is  the  Spirit  also  that,  together  with  the  water 
and  blood,  beareth  witness  of  the  truth  of  his  coming ; 
because  the  Spirit  is  truth ;  and  so  a  fit  and  unexcep- 
tionable witness.    For  there  are  three  that  bear  record 
of  his  coming ;  the  Spirit,  which  he  promised  to  send, 
and  which  was  since  shed  forth  upon  us  in  the  form 
of  cloven  tongues,  and  in  various  gifts ;  the  baptism 
of  water,  wherein  God  testified  '  this  is  my  beloved 
Son ;'  and  the  shedding  of  his  blood,  accompanied  with 
his  resurrection,  whereby  he  became  the  most  faith- 
ful martyr,  or  witness,  of  this  truth.    And  these  three, 
the  spirit,  the  baptism,  and  passion  of  Christ,  agree 
in  witnessing  one  and-the  same  thing  (namely,  that 
the  Son  of  God  is  come) ;  and,  therefore,  their  evi- 
dence is  strong :  for  the  law  requires  but  two  con- 
I  senting  witnesses,  and  here  we  have  three :  and  if 
!  we  receive  the  witness  of  men,  the  threefold  witness  of 
God,  which  he  bare  of  his  Son,  by  declaring  at  his 
baptism  'this  is  my  beloved  Son,'  by  raising  him 
from  the  dead,  and  by  pouring  out  his  Spirit  on  us 
is  greater;  and,  therefore,  ought  to  be  more  readily 
received." 

While  the  Latin  Church  was  corrupting  the  pre- 
ceding text,  the  Greek  Church  was  doing  the  same 
to  St.  Paul's  1st  Epistle  to  Timothy  iii.  16.  Great 
is  the  mystery  of  godliness,  God  manifest  in  the  flesh. 


254  SIR  ISAAC   NEWTON. 

According  to  Sir  Isaac,  this  reading  was  effected  by 
changing  b  into  ec,  the  abbreviation  of  e**,  and  after 
proving  this  by  a  learned  and  ingenious  examination 
of  ancient  manuscripts,  he  concludes  that  the  read- 
ing should  be  Great  is  the  mystery  of  Godliness  who 
(viz.  our  Saviour)  was  manifest  in  the  flesh.  \ 

As  this  learned  dissertation  had  the  effect  of  de- 
priving the  defenders  of  the  doctrine  of  the  Trinity 
of  the  aid  of  two  leading  texts,  Sir  Isaac  Newton  has 
been  regarded  as  an  Antitririitarian ;  but  such  a  con- 
clusion is  not  warranted  by  any  thing  which  he  has 
published  ;*  and  he  distinctly  warns  us,  that  his  ob- 
ject was  solely  to  "  purge  the  truth  of  things  spu- 
rious." We  are  disposed,  on  the  contrary,  to  think 
that  he  declares  his  belief  in  the  doctrine  of  the 
Trinity  when  he  says,  "  In  the  eastern  nations,  and 
for  a  long  time  in  the  western,  the  faith  subsisted 
without  this  text ;  and  it  is  rather  a  danger  to  reli- 
gion than  an  advantage,  to  make  it  now  lean  upon  a 
bruised  reed.  There  cannot  be  better  service  done 
to  the  truth  than  to  purge  it  of  things  spurious ;  and 
therefore,  knowing  your  prudence  and  calmness  of 
temper,  I  am  confident  I  shall  not  offend  you  by  tell- 
ing you  my  mind  plainly ;  especially  since  it  is  no 
article  of  faith,  no  point  of  discipline,  nothing  but  a 
criticism  concerning  a  text  of  Scripture  which  I  am 
going  to  write  about."  The  word  faith  in  the  pre- 
ceding passage  cannot  mean  faith  in  the  Scriptures  in 
general,  but  faith  in  the  particular  doctrine  of  the 
Trinity ;  for  it  is  this  article  of  faith  only  to  which 
the  author  refers  when  he  deprecates  its  leaning  on 
a  bruised  reed.  But,  whatever  be  the  meaning  of 
this  passage,  we  know  that  Sir  Isaac  was  greatly 

*  M.  Biot  has  well  remarked  that  there  is  absolutely  nothing  in  the 
writings  of  Newton  to  justify,  or  even  to  authorize,  the  idea  that  he  was 
an  Antitrinitarian.  This  passage  is  strangely  omitted  in  the  English 
translation  of  Blot's  Life  of  Newton.  We  do  not  know  upon  what  au- 
thority Dr.  Thomson  states,  in  his  History  of  the  Royal  Society,  that 
Newton  "  did  not  believe  in  the  Trinity,"  and  that  Dr.  Horsley  considered 
Newton's  papers  unfit  for  publication,  because  they  contained  proofs  of 
his  hostility  to  that  doctrine. 


LEXICON  PROPHETICITM.  255 

offended  at  Mr.  Whiston  for  having  represented  him 
as  an  Arian ;  and  so  much  did  he  resent  the  conduct 
of  his  friend  in  ascribing  to  him  heretical  opinions, 
that  he  would  not  permit  him  to  be  elected  a  Fellow 
of  the  Royal  Society  while  he  was  President.* 

The  only  other  religious  works  which  were  com- 
posed by  Sir  Isaac  Newton  were  his  Lexicon  Pro- 
pheticum,  to  which  was  added  a  Dissertation  on  the 
sacred  cubit  of  the  Jews,  and  Four  Letters  addressed 
to  Dr.  Bentley  i  containing  some  arguments  in  proof  of 
a  Deity. 

The  Lexicon  Propheticum  was  left  incomplete,  and 
has  not  been  published ;  but  the  Latin  Dissertation 
which  was  appended  to  it,  in  which  he  shows  that 
the  cubit  was  about  26£  Roman  unciae,  was  published 
in  1737  among  the  Miscellaneous  Works  of  Mr.  John 
Greaves. 

Upon  the  death  of  the  Honourable  Robert  Boyle, 
on* the  30th  of  December,  1691,  it  was  found,  by  a 
codicil  to  his  will,  that  he  had  left  a  revenue  of  507. 
per  annum  to  establish  a  lectureship,  in  which  eight 
discourses  were  to  be  preached  annually  in  one  of 
the  churches  of  the  metropolis,  in  illustration  of  the 
evidences  of  Christianity,  and  in  opposition  to  the 
principles  of  infidelity.  Dr.  Bentley,  though  a  very 
young  man,  was  appointed  to  preach  the  first  course 
of  sermons,  and  the  manner  in  which  he  discharged 
this  important  duty  gave  the  highest  satisfaction,  not 
only  to  the  trustees  of  the  lectureship,  but  to  the 
public  in  general.  In  the  first  six  lectures  Bentley 
exposed  the  folly  of  atheism  even  in  reference  to  the 
present  life,  and  derived  powerful  arguments  for  the 
existence  of  a  Deity  from  the  faculties  of  the  soul, 
and  the  structure  and  functions  of  the  human  frame 
In  order  to  complete  his  plan,  he  proposed  to  devote 
his  seventh  and  eighth  lectures  to  the  demonstration 
of  a  Divine  Providence  from  the  physical  constitu- 

*  Whiston's  Memoirs  of  his  own  Life,  p.  178,  249,  250     Edit    #8   J 


256  SIR   ISAAC   NEWTON. 

tion  of  the  universe,  as  established  in  the  Principia. 
In  order  to  qualify  himself  for  this  task,  he  received 
from  Sir  Isaac  written  directions  respecting  a  list  of 
books  necessary  to  be  perused  previous  to  the  study 
of  that  work  ;*  and  having  made  himself  master  of 
the  system  which  it  contained,  he  applied  it  with 
irresistible  force  of  argument  to  establish  the  ex- 
istence of  an  overruling  mind.  Previous  to  the  pub- 
lication of  these  lectures,  Bentley  encountered  a 
difficulty  which  he  was  not  able  to  solve,  and  he 
prudently  transmitted  to  Sir  Isaac  during  1692  a 
series  of  queries  on  the  subject.  This  difficulty  oc- 
curred in  an  argument  urged  by  Lucretius,  to  prove 
the  eternity  of  the  world  from  an  hypothesis  of  de- 
riving the  frame  of  it  by  mechanical  principles  from 
matter  endowed  with  an  innate  power  of  gravity,  and 
evenly  scattered  throughout  the  heavens.  Sir  Isaac 
'willingly  entered  upon  the  consideration  of  the  sub- 
>>*ct,  and  transmitted  his  sentiments  to  Dr.  Bentley 
in  the  four  letters  which  have  been  noticed  in  a  pre- 
ceding chapter. 

In  the  firstf  of  these  letters  Sir  Isaac  mentions 
that  when  he  wrote  his  treatise  about  our  system, 
viz.  the  Third  Book  of  the  Principia,  "  he  had  an 
eye  upon  such  principles  as  might  work,  with  con- 
sidering men,  for  the  belief  of  a  Deity,  and  he  ex- 
presses his  happiness  that  it  has  been  found  useful 
for  that  purpose.  In  answering  the  first  query  of 
Dr.  Bentley,  the  exact  import  of  which  we  do  not 
know,  he  states,  that,  if  matter  were  evenly  diffused 
through  a  finite  space,  and  endowed  with  innate 
gravity,  it  would  fall  down  into  the  middle  of  the 
space,  and  form  one  great  spherical  mass ;  but  if  it 
were  diffused  through  an  infinite  space,  some  of  it 
would  collect  into  one  mass,  and  some  into  another, 

*  Dr.  Monk's  Life  of  Bentley,  p.  31. 

t  Dated  December  10th,  1692.  This  letter  is  endorsed,  in  Bentley's 
hand,  "Mr.  Newton's  answer  to  some  queries  sent  by  me  after  I  had 
preached  my  two  last  sermons." — Monk's  Life  of  Bentley,  p.  34.  note. 


LETTERS    TO    DR.    BENTLEY.  257 

so  as  to  form  an  infinite  number  of  great  masses. 
In  this  manner  the  sun  and  stars  might  be  formed  if 
the  matter  were  of  a  lucid  nature.  But  he  thinks  it 
inexplicable  by  natural  causes,  and  to  be  ascribed  to 
the  counsel  and  contrivance  of  a  voluntary  Agent, 
that  the  matter  should  divide  itself  into  two  sorts, 
part  of  it  composing  a  shining  body  like  the  sun,  and 
part  an  opaque  body  like  the  planets.  Had  a  natural 
and  blind  cause,  without  contrivance  and  design, 
placed  the  earth  in  the  centre  of  the  moon's  orbit, 
and  Jupiter  in  the  centre  of  his  system  of  satellites, 
and  the  sun  in  the  centre  of  the  planetary  system, 
the  sun  would  have  been  a  body  like  Jupiter  and  the 
earth,  that  is,  without  light  and  heat,  and  conse- 
quently he  knows  no  reason  why  there  is  only  one 
body  qualified  to  give  light  CLid  heat  to  all  the  rest, 
but  because  the  Author  of  the  system  thought  it  con- 
venient, and  because  one  was  sufficient  to  warm 
and  enlighten  all  the  rest. 

To  the  second  query  of  Dr.  Bentley,  he  replies 
that  the  motions  which  the  planets  now  have  could 
not  spring  from  any  natural  cause  alone,  but  were 
impressed  by  an  intelligent  Agent.  "  To  make  such 
a  system  with  all  its  motions  required  a  cause  which 
understood  and  compared  together  the  quantities  of 
matter  in  the  several  bodies  of  the  sun  and  planets, 
and  the  gravitating  powers  resulting  from  thence ; 
the  several  distances  of  the  primary  planets  from 
the  sun,  and  of  the  secondary  ones  from  Saturn  Ju- 
piter, and  the  earth,  and  the  velocities  with  which 
those  planets  could  revolve  about  those  quantities 
of  matter  in  the  central  bodies ;  and  to  compare  and 
adjust  all  these  things  together  in  so  great  a  variety 
of  bodies,  argues  that  cause  to  be  not  blind  and  for- 
tuitous, but  very  well  skilled  in  mechanics  and  geo- 
metry." 

In  "the  second*  letter,  he  admits  that  the  spherical 

*  Dated  Jan.  17th,  1692-3 

Y2 


258  SIR   ISAAC   NEWTON. 

mass  formed  by  the  aggregation  of  particles  would 
affect  the  figure  of  the  space  in  which  the  matter 
was  diffused,  provided  the  matter  descends  directly 
downwards  to  that  body,  and  the  body  has  no  diurnal 
rotation ;  but  he  states,  that  by  earthquakes  loosen- 
ing the  parts  of  this  solid,  the  protuberance  might 
sink  a  little  by  their  weight,  and  the  mass  by  degrees 
approach  a  spherical  figure.  He  then  proceeds  to 
correct  an  error  of  Dr.  Bentley's  in  supposing  that 
all  infinites  are  equal.  He  admits  that  gravity  might 
put  the  planets  in  motion,  but  he  maintains  that, 
without  the  Divine  power,  it  could  never  give  them 
such  a  circulating  motion  as  they  have  about  the 
sun,  because  a  proper  quantity  of  a  transverse  mo- 
tion is  necessary  for  this  purpose  ;  and  he  concludes 
that  he  is  compelled  to  ascribe  the  frame  of  this 
system  to  an  intelligent  Agent. 

The  third  letter  contains  opinions  confirming  or 
correcting  several  positions  which  Dr.  Bentley  had 
laid  down,  and  he  concludes  it  with  a  curious  exam- 
ination of  the  opinion  of  Plato,  that  the  motion  of 
the  planets  is  such  as  if  they  had  been  ail  created 
by  God  in  some  region  very  remote  from  our  sys- 
tem, and  let  fall  from  thence  towards  the  sun,  their 
falling  motion  being  turned  aside  into  a  transverse 
one  whenever  they  arrived  at  their  several  orbits. 
Sir  Isaac  shows  that  there  is  no  common  place  such 
as  thai  conjectured  by  Plato,  provided  the  gravi- 
tating power  of  the  sun  remains  constant ;  but  that 
Plato's  affirmation  is  true  if  we  suppose  the  gravi 
tatmg  power  of  the  sun  to  be  doubled  at  that  mo- 
ment of  time  when  they  all  arrive  at  their  several 
orbits.  "  If  we  suppose,"  says  he,  "  the  gravity  of 
all  the  planets  towards  the  sun  to  be  of  such  a  quan- 
tity as  it  really  is,  and  that  the  motions  of  the 
planets  are  turned  upwards,  every  planet  will  ascend 
to  twice  its  height  from  the  sun.  Saturn  will  as- 
cend till  he  be  twice  as  high  from  the  sun  as  he  is 
at  present,  and  no  higher;  Jupiter  will  ascend  as 


LETTERS    TO   DR.   BENTLEY.  259 

high  again  as  at  present,  that  is,  a  little  above  the 
orb  of  Saturn;   Mercury  will  ascend  to  twice  his 
present  height,  that  is,  to  the  orb  of  Venus ;  and  so 
of  the  rest ;  and  then,  by  falling  down  again  from 
the  places  to  which  they  ascended,  they  will  arise 
i  again  at  their  several  orbs  with  the  same  velocities 
they  had  at  first,  and  with  which  they  now  revolve. 
"  But  if  so  soon  as  their  motions  by  which  they 
•  revolve  are  turned  upwards,  the  gravitating  power 
!  of  the  sun,  by  which  their  ascent  is  perpetually  re- 
tarded, be  diminished  by  one-half,  they  will  now 
ascend  perpetually,  and  all  of  them,  at  all  equal  dis- 
tances from  the  sun,  will  be  equally  swift.    Mer- 
cury, when  he  arrives  at  the  orb  of  Venus,  will  be 
as  swift  as  Venus ;   and  he  and  Venus,  when  they 
arrive  at  the  orb  of  the  earth,  will  be  as  swift  as  the 
earth ;  and  so  of  the  rest.    If  they  begin  all  of  them 
to  ascend  at  once,  and  ascend  in  the  same  line,  they 
i  will  constantly,  in  ascending,  become  nearer  and 
I  nearer  together,  and  their  motions  will  constantly 
[approach  to   an  equality,   and  become  at    length 
slower  than  any  motion  assignable.    Suppose,  there- 
fore, that  they  ascended  till  they  were  almost  con- 
tiguous, and  their  motions  inconsiderably  little,  and 
(that  all  their  motions  were  at  the  same  moment  of 
time  turned  back  again,  or,  which  comes  almost  to 
ithe  same  thing,  that  they  were  only  deprived  of  their 
I  motions,  and  let  fall  at  that  time,  they  would  all  at 
once  arrive  at  their  several  orbs,  each  with  the  ve- 
rt locity  it  had  at  first ;  and  if  their  motions  were  then 
I  turned  sideways,  and  at  the  same  time  the  gravi- 
tating power  of  the  sun  doubled,  that  it  might  be 
strong  enough  to  retain  them  in  their  orbs,  they 
would  revolve  in  them  as  before  their  ascent.    But 
if  the  gravitating  power  of  the  sun  was  not  doubled, 
they  would  go  away  from  their  orbs  into  the  highest 
heavens  in  parabolical  lines."* 

*  "  These  things,"  says  he,  "  follow  from  my  Princip.  Matk.  lib.  i. 
prop.  33,  34,  35,  36  " 


260  SIR    ISAAC   NEWTON. 

In  the  fourth  letter*  he  states,  that  the  hypothesi 
that  matter  is  at  first  evenly  diffused  through  th 
universe  is  in  his  opinion  inconsistent  with  th 
hypothesis  of  innate  gravity  without  a  supernature 
power  to  reconcile  them,  and  therefore  it  infers 
Deity.  "  For  if  there  be  innate  gravity,  it  is  impos 
sible  now  for  the  matter  of  the  earth  and  all  th 
planets  and  stars  to  fly  up  from  them,  and  becom 
evenly  spread  throughout  all  the  heavens  without 
supernatural  power;  and  certainly  that  which  ca: 
never  be  hereafter  without  a  supernatural  powei 
could  never  be  heretofore  without  the  same  power. 

These  letters,  of  which  we  have  endeavoured  t 
give  a  brief  summary,  will  well  repay  the  mos 
attentive  perusal  by  the  philosopher  as  well  as  th 
divine.  They  are  written  with  much  perspicuity  o 
language  and  great  power  of  thought,  and  the; 
contain  results  which  incontestably  prove  that  thei 
author  was  fully  master  of  his  noblest  faculties 
and  comprehended  the  profoundest  parts  of  his  ow: 
writings.! 

The  logical  acuteness,  the  varied  erudition,  an 
the  absolute  freedom  from  all  prejudice  which  shin 
throughout  the  theological  writings  of  Newtor 
might  have  protected  them  from  the  charge  of  ha\ 
ing  been  written  in  his  old  age,  and  at  a  time  whe 
a  failure  -of  mind  was  supposed  to  have  unfitted  hir 
for  his  mathematical  investigations.  But  it  is  fortu 
nate  for  his  reputation,  as  well  as  for  the  interest 
of  Christianity,  that  we  have  been  able  to  prove  th 
incorrectness  of  such  insinuations,  and  to  exhibi 
the  most  irrefragable  evidence  that  all  the  theologicc 

*  Dated  February  llth,  1693. 

t  The  originals  of  these  four  letters  to  Bentley  "  were  given  by  D 
Richard  Bentley  to  Cumberland,  his  nephew,  and  executor,  while  a  sti 
dent  at  Trinity  College,  and  were  printed  by  him  in  a  separate  pamphh 
in  1756.  This  publication  was  reviewed  by  Dr.  Samuel  Johnson  in  th 
Literary  Magazine,  vol.  i.  p.  89.  See  Johnson's  Works,  vol.  ii.  p.  32i 
The  original  letters  are  preserved  in  Trinity  College,  to  which  societ 
they  were  given  by  Cumberland  a  short  time  before  his  death."— Monk' 
Life  of  Bentley,  p.  33,  note. 


THEOLOGICAL    STUDIES.  261 

writings  of  Newton  were  composed  in  the  vigour 
)f  his  life,  and  before  the  crisis  of  that  bodily  dis- 
>rder  which  is  supposed  to  have  affected  his  reason. 
The  able  letters  to  Dr.  Bentley  were  even  written 
n  the  middle  of  that  period  when  want  of  sleep  and 
ippetite  had  disturbed  the  serenity  of  his  mind,  and 
mable  us  to  prove  that  this  disturbance,  whatever 
vas  its  amount,  never  affected  the  higher  functions 
)f  his  understanding. 

When  a  philosopher  of  distinguished  eminence, 
ind  we  believe  not  inimical  to  the  Christian  faith, 
as  found  it  necessary  to  make  a  laboured  apology 
or  a  man  like  Newton  writing  on  theological  sub- 
ects,  and  has  been  led  to  render  that  apology  more 
omplete  by  referring  this  class  of  his  labours  to  a 
nind  debilitated  by  age  and  weakened  by  its  pre- 
ious  aberrations,  it  may  be  expected  from  an  Eng- 
sh  biographer,  and  one  who  acknowledges  the 
mportance  of  revealed  truth,  and  the  paramount 
nterest  of  such  subjects  above  all  secular  studies, 
o  suggest  the  true  origin  of  Newton's  theological 
iquiries. 

When  a  mind  of  great  and  acknowledged  power 
rst  directs  its  energies  to  the  study  of  the  material 
niverse,  no  indications  of  order  attract  his  notice, 
rid  no  proofs  of  design  call  forth  his  admiration, 
n  the  starry  firmament  he  sees  no  bodies  of  stupen- 
ous  magnitude,  and  no  distances  of  immeasurable 
jan.  The  two  great  luminaries  appear  vastly  in- 
'edor  in  magnitude  to  many  objects  around  him,  and 
le  greatest  distances  in  the  heavens  seem  even  in- 
erior  to  those  which  his  own  eye  can  embrace  on 
he  surface  of  the  earth.  The  planets,  when  ob- 
erved  with  care,  are  seen  to  have  a  motion  among 
he  fixed  stars,  and  to  vary  in  their  magnitude  and 
istances,  but  these  changes  appear  to  follow  no 
aw.  Sometimes  they  move  to  the  east,  sometimes 
o  the  west,  sometimes  towards  the  north,  and 
ometimes  towards  the  south,  and  at  other  times 


262  SIR   ISAAC   NEWTON. 


, 


they  are  absolutely  stationary.  No  system,  in  short, 
appears,  and  no  general  law  seems  to  direct  their 
motions.  By  the  observations  and  inquiries  of 
astronomers,  however,  during  successive  ages,  a 
regular  system  has  been 'recognised  in  this  chaos  of 
moving  bodies,  and  the  magnitudes,  distances,  and 
revolutions  of  every  planet  which  composes  it  has 
been  determined  with  the  most  extraordinary  accu- 
racy. Minds  fitted  and  prepared  for  this  species  of 
inquiry  are  capable  of  understanding  the  great 
variety  of  evidence  by  which  the  truth  of  the  plan-  * 
etary  system  is  established ;  but  thousands  of  indi- 
viduals who  are  even  distinguished  in  other  branches 
of  knowledge  are  incapable  of  such  researches,  and 
view  with  a  skeptical  eye  the  great  and  irrefragable 
truths  of  astronomy. 

That  the  sun  is  stationary  in  the  centre  of  our 
system, — that  the  earth  moves  round  the  sun,  and 
round  its  own  axis, — that  the  earth  is  8000  miles  in 
diameter,  and  the  sun  one  hundred  and  ten  times  as 
large,— that  the  earth's  orbit  is  190  millions  of  miles 
in  breadth, — and  that  if  this  immense  space  were 
filled  with  light,  it  would  appear  only  like  a  luminous 
point  at  the  nearest  fixed  star, — are  positions  abso- 
lutely unintelligible  and  incredible  to  all  who  have 
not  carefully  studied  the  subject.  To  millions  of 
our  species,  then,  the  great  book  of  nature  is  ab- 
solutely sealed,  though  it  is  in  the  power  of  all  to 
unfold  its  pages,  and  to  peruse  those  glowing  pas- 
sages which  proclaim  the  power  and  wisdom  of  its 
mighty  Author. 

The  book  of  revelation  exhibits  to  us  the  same 
peculiarities  as  that  of  nature.  To  the  ordinary 
eye  it  presents  no  immediate  indications  of  its 
Divine  origin.  Events  apparently  insignificant- 
supernatural  interferences  seemingly  unnecessary 
— doctrines  almost  contradictory — and  prophecies 
nearly  unintelligible  occupy  its  pages.  The  history 
of  the  fall  of  man — of  the  introduction  of  moral 


THEOLOGICAL   STUDIES.  263 

and  physical  evil — the  prediction  of  a  Messiah — the 
actual  advent  of  our  Saviour — his  instructions — his 
miracles — his  death — his  resurrection — and  the  sub- 
sequent propagation  of  his  religion  by  the  unlettered 
;ishermen  of  Galilee,  are  each  a  stumblingblock  to 
;:he  wisdom  of  this  world.  The  youthful  and  vigor- 
ous mind,  when  first  summoned  to  peruse  the  Scrip- 
;ures,  turns  from  them  with  disappointment.  It 
recognises  in  them  no  profound  science — no  secular 
pisdom — no  Divine  eloquence — no  disclosures  of 
jiature's  secrets — no  direct  impress  of  an  Almighty 
pand.  But,  though  the  system  of  revealed  truth 
[which  this  book  contains  is,  like  that  of  the  universe, 
Concealed  from  common  observation,  yet  the  labours 
JDf  centuries  have  established  its  Divine  origin,  and 
developed  in  all  its  order  and  beauty  the  great  plan 
pf  human  restoration.  In  the  chaos  of  its  incidents 
we  discover  the  whole  history  of  our  species, 
whether  it  is  delineated  in  events  that  are  past  or 
shadowed  forth  in  those  which  are  to  come, — from 
;he  creation  of  man  and  the  origin  of  evil,  to  the 
extinction  of  his  earthly  dynasty  and  the  commence- 
ment of  his  immortal  career. 
The  antiquity  and  authenticity  of  the  books  which 

ompose  the  sacred  canon, — the  fulfilment  of  its 
prophecies, — the  miraculous  works  of  its  founder, — 
his  death  and  resurrection,  have  been  demonstrated 
jto  all  who  are  capable  of  appreciating  the  force  of 
historical  evidence;  and  in  the  poetical  and  prose 
|bompositions  of  the  inspired  authors  we  discover  a 
system  of  doctrine  and  a  code  of  morality  traced  in 
characters  as  distinct  and  legible  as  the  most  unerr- 
ing truths  in  the  material  world.  False  systems  of 
religion  have  indeed  been  deduced  from  the  sacred 
record, — as  false  systems  of  the  universe  have 
sprung  from  the  study  of  the  book  of  nature, — but 
the  very  prevalence  of  a  false  system  proves  the 
existence  of  one  that  is  true ;  and  though  the  two 

classes   of   facts  necessarily  depend  on  different 


264  SIR  ISAAC   NEWTON. 

kinds  of  evidence,  yet  we  scruple  not  to  say  that 
the  Copernican  system  is  not  more  demonstrably 
true  than  the  system  of  theological  truth  contained 
in  the  Bible.  If  men  of  high  powers,  then,  are  still 
found,  who  are  insensible  to  the  evidence  which 
sustains  the  system  of  the  universe,  need  we  won- 
der that  there  are  others  whose  minds  are  shut 
against  the  effulgent  evidence  which  intrenches  the 
strongholds  of  our  faith. 

If  such,  then,  is  the  character  of  the  Christian 
faith,  we  need  not  be  surprised  that  it  was  embraced 
and  expounded  by  such  a  genius  as  Sir  Isaac  New- 
ton. Cherishing  its  doctrines,  and  leaning  on  its 
promises,  he  felt  it  his  duty,  as  it  was  his  pleasure, 
to  apply  to  it  that  intellectual  strength  which  had 
successfully  surmounted  the  difficulties  of  the  ma- 
terial universe.  The  fame  which  that  success  pro- 
cured him  he  could  not  but  feel  to  be  the  breath  of 
popular  applause,  which  administered  only  to  his 
personal  feelings  ;  but  the  investigation  of  the  sacred 
mysteries,  while  it  prepared  his  own  mind  for  its 
final  destiny,  was  calculated  to  promote  the  spiritual 
interests  of  thousands.  This  noble  impulse  he  did 
not  hesitate  to  obey,  and  by  thus  uniting  philosophy 
with  religion,  he  dissolved  the  league  which  genius 
had  formed  with  skepticism,  and  added  to  the  cloud 
of  witnesses  the  brightest  name  of  ancient  or  of 
modern  times. 


HIS    SCALE    OF  HEAT.  265 


CHAPTER  XVII. 

Tfte  minor  Discoveries  and  Inventions  of  Neivton— His  Researches  on 
Heat— On  Fire  and  Flame— On  Elective  Attraction— On  the  Struc- 
ture of  Bodies— His  supposed  Attachment  to  Alchymy—His  Hypothe- 
sis respecting  Ether  as  the  Cause  of  Light  and  Gravity— On  the  Ex- 
citation of  Electricity  in  ^lass—His  Reflecting  Sextant  invented 
before  17Q&— His  Reflecting  Microscope— His  Prismatic  Reflector* as  a 
Substitute  for  the  small  Speculum  of  Reflecting  Telescopes— Hit 
Method  of  varying  the  Magnifying  Power  of  Newtonian  Telescopes 
— His  Experiments  on  Impressions  on  the  Retina. 

IN  the  preceding  chapters  we  have  given  an  ac- 
count of  the  principal  labours  of  Sir  Isaac  Newton ; 
but  there  still  remain  to  be  noticed  several  of  his 
minor  discoveries  and  inventions,  which  could  not 
properly  be  introduced  under  any  general  head. 

The  most  important  of  these,  perhaps,  are  his 
chymical  researches,  which  he  seems  to  have  pur- 
sued with  more  or  less  diligence  from  the  time 
when  he  first  witnessed  the  practical  operations  of 
chymistry  during  his  residence  at  the  apothecary's 
at  Grantham.  .  His  first  chymical  experiments  were 
probably  made  on  the  alloys  of  metals,  for  the  pur- 
pose of  obtaining  a  good  metallic  composition  for 
the  specula  of  reflecting  telescopes.  In  his  paper 
on  thin  plates  he  treats  of  the  combinations  of  solids 
and  fluids ;  but  he  enters  more  largely  on  these  and 
other  subjects  in  the  queries  published  at  the  end 
of  his  Optics. 

One  of  his  most  important  chymical  papers  is 
his  Tabula  quantltatum  et  graduum  caloris,  which 
was  published  in  the  Philosophical  Transactions. 
This  short  paper  contains  a  comparative  scale  of 
temperature  from  that  of  melting  ice  to  that  of  a 
small  kitchen  coal-fire.  The  following  are  the 
principal  points  of  the  scale,  the  intermediate 
Z 


266  SIR   ISAAC   NEWTON. 

degrees  of  heat  having  been  determined  with  great 
care. 

Degrees  Equal  Parts 

of  H«t.  of  Heat. 

0  0  Freezing  point  of  water. 

1  12  Blood-heat. 

2  24  Heat  of  melting  wax. 

3  48  Melting  point  of  equal  parts  of  tin 

and  bismuth. 

4  96  Melting  point  of  lead. 

5  192  Heat  of  a  small  coal-fire. 

The  first  column  of  this  table  contains  the  degrees! 
of  heat  in  arithmetical  progression,  and  the  second! 
in  geometrical  progression, — the  second  degree  being! 
twice  as  great  as  the  first,  and  so  on.  It  is  obvious 
from  this  table,  that  the  heat  at  which  equal  parts 
of  tin  and  bismuth  melt  is  four  times  greater  than 
that  of  blood-heat,  the  heat  of  melting  lead  eight 
times  greater,  and  the  heat  of  a  small  coal-fire  six- 
teen times  greater.  » 

This  table  was  constructed  by  the  help  of  a  ther-s 
mometer,  and  of  red-hot  iron.  By  the  former  he! 
measured  all  heats  as  far  as  that  of  melting  tinji 
and  by  the  latter  he  measured  all  the  higher  heats. 
For  the  heat  which  heated  iron  loses  in  a  given  time 
is  as  the  total  heat  of  the  iron ;  and  therefore,  if  the 
times  of  cooling  are  taken  equal,  the  heats  will  be 
in  a  geometrical  progression,  and  may  therefore  be 
easily  found  by  a  table  of  logarithms. 

He  found  by  a  thermometer  constructed  with  lin- 
seed oil,  that  if  the  oil,  when  the  thermometer  was 
placed  in  melting  snow,  occupied  a  space  of  1000 
parts,  the  same  oil,  rarefied  with  one  degree  of  heat, 
or  that  of  the  human  body,  occupied  a  space  of 
10256 ;  in  the  heat  of  water  beginning  to  boil,  a 
space  of  10705 ;  in  the  heat  of  water  boiling  vio- 
lently, 10725 ;  in  the  heat  of  melted  tin  beginning  tc 
cool,  and  putting  on  the  consistency  of  an  amalgam. 


HIS    SCALE    OF   HEAT.  267 

11516,  and  when  the  tin  had  become  solid,  11496. 
Hence  the  oil  was  rarefied  in  the  ratio  of  40  to  39 
by  the  heat  of  the  human  body  ;  of  15  to  14  by  the 
heat  of  boiling  water;  of  15  to  13  in  the  heat  of 
melting  tin  beginning  to  solidify ;  and  of  23  to  20  in 
the  same  tin  when  solid.  The  rarefaction  of  air 
was,  with  the  same  heat,  ten  times  greater  than  that 
of  oil,  and  the  rarefaction  of  oil  fifteen  times  greater 
than  that  of  spirit  of  wine.  By  making  the  heats 
of  oil  proportional  to  its  rarefaction,  and  by  calling 
the  heat  of  the  human  body  12  parts,  we  obtain  the 
heat  of  water  beginning  to  boil,  33  ;  of  water  boil- 
ing violently,  34 ;  of  melted  tin  beginning  to  solidify, 
72 ;  and  of  the  same  become  solid,  70. 

Sir  Isaac  then  heated  a  sufficiently  thick  piece 
bf  iron  till  it  was  red-hot ;  and  having  fixed  it  in  a 
cold  place,  where  the  wind  blew  uniformly,  he  put 
upon  it  small  pieces  of  different  metals  and  other 
fusible  bodies,  and  noted  the  times  of  cooling,  till 
all  the  particles,  having  lost  their  fluidity,  grew  cold, 
and  the  heat  of  the  iron  was  equal  to  that  of  the 
human  body.  Then,  by  assuming  that  the  excesses 
of  the  heats  of  the  iron  and  of  the  solidified  par- 
ticles of  metal  above  the  heat  of  the  atmosphere, 
were  in  geometrical  progression  when  the  times 
were  in  arithmetical  progression,  all  the  heats  were 
obtained.  The  iron  was  placed  in  a  current  of  air, 
in  order  that  the  air  heated  by  the  iron  might  always 
I  be  carried  away  by  the  wind,  and  that  cold  air 
i  might  replace  it  with  a  uniform  motion;  for  thus 
equal  parts  of  the  air  were  heated  in  equal  times, 
and  received  a  heat  proportional  to  that  of  the  iron. 
But  the  heats  thus  found  had  the  same  ratio  to  one 
another  with  the  heats  found  by  the  thermometer ; 
and  hence  he  was  right  in  assuming  that  the  rare- 
factions of  the  oil  were  proportional  to  its  heats. 

Another  short  chymical  paper  by  Sir  Isaac  New- 
ton has  been  published  by  Dr.  Horsley,    It  is  enti- 


268  SIR   ISAAC   NEWTON. 

tied  De  Natura  Acidorum,  but  is  principally  occupied 
with  a  number  of  brief  opinions  on  chymical  sub- 
jects. This  paper  was  written  later  than  1687,  as  it 
bears  a  reference  to  the  Principia ;  and  the  most  im- 
portant facts  which  it  contains  seem  to  have  been 
more  distinctly  reproduced  in  the  queries  at  the  end 
of  the  Optics. 

The  most  important  of  these  queries  relate  to  fire, 
flame,  and  electric  attractions,  and  as  they  were  re- 
vised in  the  year  1716  and  1717,  they  may  be  regarded 
as  containing  the  most  matured  opinions  of  their 
author.  Fire  he  regards  as  a  body  heated  so  hot  as 
to  emit  light  copiously,  and  flane  as  a  vapour,  fume, 
or  exhalation  heated  so  hot  as  to  shine.  In  his  long 
query  on  elective  attractions,  he  considers  the  small 
particles  of  bodies  as  acting  upon  one  another  at 
distances  so  minute  as  to  escape  observation.  When 
salt  of  tartar  deliquesces,  he  supposes  that  this  arises 
from  an  attraction  between  the  saline  particles  and 
the  aqueous  particles  held  in  solution  in  the  atmos- 
phere, and  to  the  same  attraction  he  ascribes  it  that 
the  water  will  not  distil  from  the  salt  of  tartar  with- 
out great  heat.  For  the  same  reason  sulphuric  acid 
attracts  water  powerfully,  and  parts  with  it  with 
great  difficulty.  When  this  attractive  force  becomes 
very  powerful,  as  in  the  union  between  sulphuric 
acid  and  water,  so  as  to  make  the  particles  "  coalesce 
with  violence,"  and  rush  towards  one  another  with 
an  accelerated  motion,  heat  is  produced  by  the  mix- 
ture of  the  two  fluids.  In  like  manner,  he  explains 
the  production  of  flame  from  the  mixture  of  cold 
fluids, — the  action  of  fulminating  powders, — the  com- 
bination of  iron  filings  with  sulphur—and  all  the 
other  chymical  phenomena  of  precipitation,  combi- 
nation, solution,  and  crystallization,  and  the  mechan- 
ical phenomena  of  cohesion  and  capillary  attrac- 
tion. He  ascribes  hot  springs,  volcanoes,  fire-damps, 
mineral  coruscations,  earthquakes,  hot  suffocating 


ELECTIVE  ATTRACTION.  269 

exhalations,  hurricanes,  lightning,  thunder,  fiery 
meteors,  subterraneous  explosions,  land-slips,  ebul- 
litions of  the  sea,  and  waterspouts,  to  sulphureous 
steams  abounding  in  the  bowels  of  the  earth,  and 
fermenting  with  minerals,  or  escaping  into  the  atmos- 
phere, where  they  ferment  with  acid  vapours  fitted 
to  promote  fermentation. 

In  explaining  the  structure  of  solid  bodies,  he  is 
of  opinion,  "that  the  smallest  particles  of  matter 
may  cohere  by  the  strongest  attractions,  and  com- 
pose bigger  particles  of  weaker  virtue ;  and  many 
of  these  may  cohere  and  compose  bigger  particles 
whose  virtue  is  still  weaker ;  and  so  on  for  divers 
successions,  until  the  progression  end  in  the  biggest 
particles,  on  which  the  operations  in  chymistry  and 
the  colours  of  natural  bodies  depend,  and  which,  by 
adhering,  compose  bodies  of  a  sensible  magnitude. 
If  the  body  is  compact,  and  bends  or  yields  inward 
to  pression,  without  any  sliding  of  its  parts,  it  is  hard 
and  elastic,  returning  to  its  figure  with  a  force  rising 
from  the  mutual  attraction  of  its  parts.  If  the  parts 
slide  upon  one  another,  the  body  is  malleable  or  soft. 
If  they  slip  easily,  and  are  of  a  fit  size  to  be  agitated 
by  heat,  and  the  heat  is  big  enough  to  keep  them  in 
agitation,  the  body  is  fluid ;  and  if  it  be  apt  to  stick 
to  things,  it  is  humid ;  and  the  drops  of  every  fluid 
affect  a  round  figure,  by  the  mutual  attraction  of  their 
parts,  as  the  globe  of  the  earth  and  sea  affects  a 
round  figure,  by  the  mutual  attraction  of  its  parts,  by 
gravity." 

Sir  Isaac  then  supposes,  that,  as  the  attractive 
force  of  bodies  can  reach  but  to  a  small  distance  from 
them,  "  a  repulsive  virtue  ought  to  succeed ;"  and  he 
considers  such  a  virtue  as  following  from  the  reflec- 
tion of  the  rays  of  light,  the  rays  being  repelled  with- 
Dut  the  immediate  contact  of  the  reflecting  body,  and 
also  from  the  emission  of  light,  the  ray,  as  soon  as 
it  is  shaken  off  from  a  shining  body  by  the  vibrating 
motion  of  the  parts  of  the  body,  getting  beyond  the 
Z2 


270  SIR  ISAAC  NEWTON. 

reach  of  attraction,  and  being  driven  away  with  ex*' 
ceeding  great  velocity  by  the  force  of  reflection.* 

Many  of  the  chymical  views  which  Sir  Isaac  thus 
published  in  the  form  of  queries  were  in  his  own 
lifetime  illustrated  and  confirmed  by  Dr.  Stephen 
Hales,  in  his  book  on  Vegetable  Statics^a,  work  of 
great  originality,  which  contains  the  germ  of"  some 
of  the  finest  discoveries  in  modern  chynustry. 

Although  there  is  no  reason  to  suppose  that  Sir 
Isaac  Newton  was  a  believer  in  the'  doctrines  of 
alchymy,  yet  we  are  informed  by  the  Reverend  Mr. 
Law  that  he  had  been  a  diligent  student  of  Jacob 
Behmen's  writings,  and  that  there  were  found  among 
his  papers  copious  abstracts  from  them  in  his  own 
handwriting.f  He  states  also  that  Sir  Isaac,  together 
with  one  Dr.  Newton,  his  relation,  had,  in  the  earlier 
part  of  his  life,  set  up  furnaces,  and  were  for  several 
months  at  work  in  quest  of  the  philosopher's  tinc- 
ture. These  statements  may  receive  some  confir- 
mation from  the  fact,  that  there  exist  among  the 
Portsmouth  papers  many  sheets,  in  Sir  Isaac's  own 
writing,  of  Flammel's  Explication  of  Hieroglyphic 
Figures,  and  in  another  hand,  many  sheets  of  Wil- 
liam Yworth's  Processus  Mysteni  Magni  Philosophi- 
cus,  and  also  from  the  manner  in  which  Sir  Isaac 
requests  Mr.  Aston  to  inquire  after  one  Borry  in 
Holland,  who  always  went  clothed  in  green,  and  who 
was  said  to  possess  valuable  secrets ;  but  Mr.  Law 
has  weakened  the  force  of  his  own  testimony,  when 

*  Mr.  Herschel,  in  his  Treatise  on  Light,  $  553,  has  maintained  that 
Newton's  Doctrine  of  Reflection  is  accordant  with  Ihe  idea  that  the 
attractive  force  extends  beyond  the  repulsive  or  reflecting  force.  In  the 
query  above  referred  to,  Sir  Isaac,  in  the  most  distinct  mauner,  places 
the  sphere  of  the  reflecting  force  without  that  of  the  attractive  one. 

t  In  a  tract  annexed  to  his  Appeal  to  all  that  doubt  or  disbelieve  the 
truths  of  the  Gospel.  See  Gent.  Mag.  1782,  vol.  lii.  p.  227,  239. 

It  is  stated  in  a  letter  of  Mr.  Law's,  quoted  in  this  magazine,  that 
Charles  I.  was  a  diligent  reader  and  admirer  of  Jacob  Behmen ;  that  ho 
sent  a  well-qualified  person  from  England  to  Goerlitz,  in  Upper  Lusatia, 
to  acquire  the  German  language,  and  to  collect  every  anecdote  he  could 
meet  with  there  relative  to  this  great  alchymist. 


HYPOTHESIS   OF   ETHER.  271 

he  asserts  that  Newton  borrowed  the  doctrine  of 
attraction  from  Behmen's  first  three  propositions  of 
eternal  nature. 

On  the  7th  December,  1675,  Sir  Isaac  Newton  com- 
municated to  the  Royal  Society  a  paper  entitled 
An  hypothesis  explaining  -properties  of  light,  in  which 
he,  for  the  first  time,  introduces  his  opinions  respect- 
ing ether,  and  employs  them  to  explain  the  nature 
of  light,  and  the  cause  of  gravity.  "He  was  in- 
duced,'1 he  says,  "to  do  this,  because  he  had  observed 
the  heads  of  some  great  virtuosos  to  run  much  upon 
hypotheses,  and  he  therefore  gave  one  which  he  was 
inclined  to  consider  as  the  most  probable,  if  he  were 
obliged  to  adopt  one."* 

This  hypothesis  seems  to  have  been  afterward  a 
subject  of  discussion  between  him  and  Mr.  Boyle,  to 
whom  he  promised  to  communicate  his  opinion  more 
fully  in  writing.  He  accordingly  addressed  to  him  a 
long  letter,  dated  February  28th,  1678-9,  in  which 
he  explains  his  views  respecting  ether,  and  employs 
them  to  account  for  the  refraction  of  light, — the  co- 
hesion of  two  polished  pieces  of  metal  in  an  exhausted 
receiver, — the  adhesion  of  quicksilver  to  glass  tubes, 
— the  cohesion  of  the  parts  of  all  bodies, — the  cause 
of  filtration, — the  phenomena  of  capillary  attraction, 
• — the  action  of  menstrua  on  bodies, — the  transmu- 
tation of  gross  compact  substances  into  aerial  ones, 
— and  the  cause  of  gravity.  From  the  language  used 
in  this  paper,  we  should  be  led  to  suppose  that  Sir 
Isaac  had  entirely  forgotten  that  he  had  formerly 
treated  the  general  subject  of  ether,  and  applied  it 
to  the  explanation  of  gravity.  "  I  shall  set  down," 
says  he,  "  one  conjecture  more  which  came  into  my 
mind  now  as  I  was  writing  this  letter ;  it  is  about  the 
cause  of  gravity"  which  he  goes  on  to  explain  ;|  and 

*  Tn  a  letter  to  Dr.  Halley,  dated  June  20th,  1686,  Sir  Isaac  refers  to 
this  paper,  and  observes,  that  it  is  only  to  be  looked  upon  as  one  of  hia 
guesses  that  he  did  not  rely  upon. 

t  See  page  2731 


SIR   ISAAC   NEWTON. 

he  concludes  by  saying,  that  "  he  has  so  little  fancy 
to  things  of  this  nature,  that,  had  not  your  encourage* 
ment  moved  me  to  it,  I  should  never,  I  think,  thus  far 
have  set  pen  to  paper  about  them." 

These  opinions,  however,  about  the  existence  of 
ether,  Newton  seems  to  have  subsequently  re- 
nounced; for  in  the  manuscript  in  the  possession 
of  Dr.  J.  C.  Gregory,  which  we  have  already  men- 
tioned, and  which  was  written  previous  to  1702,  he 
states,  that  ether  is  neither  obvious  to  our  senses, 
nor  supported  by  any  arguments,  but  is  a  gratuitous 
assumption,  which,  if  we  are  to  trust  to  reason  and 
to  our  senses,  must  be  banished  from  the  nature  of 
things ;  and  he  goes  on  to  establish,  by  various  argu* 
ments,  the  validity  of  this  opinion.  This  renuncia- 
tion of  his  former  hypothesis  probably  arose  from 
his  having  examined  more  carefully  some  of  the 
phenomena  which  he  endeavoured  to  explain  by  it. 
Those  of  capillary  attraction,  for  example,  he  had 
ascribed  to  the  ether  "  standing  rarer  in  the  very  sen- 
sible cavities  of  the  capillary  tubes  than  without 
them,"  whereas  he  afterward  discovered  their  true 
cause,  and  ascribed  them  to  the  reciprocal  attraction 
of  the  tube  and  the  fluid.  But,  however  this  may 
be,  there  can  be  no  doubt  that  he  resumed  his  early 
opinions  before  the  publication  of  his  Optics,  which 
may  be  considered  as  containing  his  views  upon  this 
subject. 

The  queries  which  contain  these  opinions  are  the 
18th-24th,  all  of  which  appeared  for  the  first  time  in 
the  second  English  edition  of  the  Optics.  If  a  body 
is  either  heated  or  loses  its  heat  when  placed  in 
vacuo,  he  ascribes  the  conveyance  of  the  heat  in 
both  cases  "  to  the  vibration  of  a  much  subtiler  me- 
dium than  air ;"  and  he  considers  this  medium  as  the 
same  with  that  by  which  light  is  refracted  and  re- 
flected, and  by  whose  vibrations  light  communicates 
heat  to  bodies,  and  is  put  into  fits  of  easy  reflectiou 
and  transmission. 


HYPOTHESIS    OF   ETHER.  273 

This  ethereal  medium,  according  to  our  author,  is 
exceedingly  more  rare  and  more  elastic  than  air. 
It  pervades  all  bodies,  and  is  expanded  through  all 
the  heavens.  It  is  much  rarer  within  the  dense 
bodies  of  the  sun,  stars,  planets,  and  comets,  than 
in  the  celestial  spaces  between  them,  and  also  more 
rare  within  glass,  water,  &c.  than  in  the  free  and 
open  spaces  void  of  air  and  other  grosser  bodies. 
In  passing  out  of  glass,  water,  &c.  and  other  dense 
bodies  into  empty  space,  it  grows  denser  and  denser 
by  degrees,  and  this  gradual  condensation  extends 
to  some  distance  from  the  bodies.  Owing  to  its 
great  elasticity,  and,  consequently,  its  efforts  to 
spread  in  all  directions,  it  presses  against  itself,  and, 
consequently,  against  the  solid  particles  of  bodies, 
so  as  to  make  them  continually  approach  to  one 
another,  the  body  being  impelled  from  the  denser 
parts  of  the  medium  towards  the  rarer  with  all  that 
power  which  we  call  gravity. 

In  employing  this  medium  to  explain  the  nature 
of  light,  Newton  does  not  suppose,  with  Descartes, 
Hooke,  Huygens,  and  others,  that  light  is  nothing 
more  than  the  impression  of  those  undulations  on 
the  retina.  He  regards  light  as  a  peculiar  substance, 
composed  of  heterogeneous  particles  thrown  off  with 
great  velocity,  and  in  all  directions,  from  luminous 
bodies ;  and  he  supposes  that  these  particles  while 
passing  through  the  ether,  excite  in  it  vibrations  or 
pulses  which  accelerate  or  retard  the  particles  of 
light,  and  thus  throw  them  into  their  alternate  fits 
of  easy  reflection  and  transmission. 

Hence,  if  a  ray  of  light  falls  upon  a  transparent 
body,  in  which  the  ether  consists  of  strata  of  varia- 
ble density,  the  particles  of  light  acted  upon  by  the 
vibrations  which  they  create  will  be  urged  with  an 
accelerated  velocity  in  entering  the  body,  while  their 
velocity  will  be  retarded  in  quitting  it.  In  this  man- 
ner he  conceives  the  phenomena  of  refraction  to  be 
produced,  and  he  shows  how  in  such  a  case  the 


274  SIR   ISAAC  NEWTON. 

refraction  would  be  regulated  by  the  law  of  the* 
sines. 

In  order  that  the  ethereal  medium  may  produce 
the  fits  of  easy  reflection  and  transmission,  he  con- 
ceives that  its  vibrations  must  be  swifter  than  light. 
He  computes  its  elasticity  to  be  490,000,000,000 
times  greater  than  that  of  air,  in  proportion  to  its 
density,  and  about  600,000,000  times  more  rare  than 
water,  from  which  he  infers  that  the  resistance 
which  it  would  oppose  to  the  motions  of  the  planets 
would  not  be  sensible  in  10,000  years.  He  considers 
that  the  functions  of  vision  and  hearing  may  be  per- 
formed chiefly  by  the  vibrations  of  this  medium, 
executed  in  the  bottom  of  the  eye,  or  in  the  auditory 
nerve  by  the  rays  of  light,  and  propagated  through 
the 'solid,  pellucid,  and  uniform  capillamenta  of  the 
optic  or  auditory  nerves  into  the  place  of  sensation ; 
and  he  is  of  opinion  that  animal  motion  may  be 
performed  by  the  vibrations  of  the  same  medium, 
excited  in  the  brain  by  the  power  of  the  will,  and 
propagated  from  thence  by  the  solid,  pellucid,  and 
uniform  capillamenta  of  the  nerves  into  the  muscles 
for  contracting  and  dilating  them. 

In  the  registers  of  the  Royal  Society  there  exist 
several  letters*  on  the  excitation  of  electricity  in 
glass,  which  were  occasioned  by  an  experiment  of 
this  kind  having  been  mentioned  in  Sir  Isaac's 
hypothesis  of  light.  The  society  had  ordered  the 
experiment  to  be  tried  at  their  meeting  of  the  16th 
December,  1675 ;  but,  in  order  to  secure  its  success, 
Mr.  Oldenburg  wrote  to  Sir  Isaac  for  a  more  par- 
ticular account  of  it.  Sir  Isaac  being  tnus  "put 
upon  recollecting  himself  a  little  farther  about  it," 
remembers  that  he  made  the  experiment  with  a 
glass  fixed  at  the  distance  of  the  ^d  of  an  inch  from 
one  end  of  a  brass  hoop,  and  only  the  ^th  of  an  inch 
from  the  other.  Small  pieces  of  thin  paper  were 

*  See  Newtoni  Opera,  by  Horsley,  vol.  iv.  p.  375-382 


REFLECTING   SEXTANT.  275 

then  laid  upon  the  table ;  when  the  glass  was  laid 
above  them  and  rubbed,  the  pieces  of  paper  leaped 
from  the  one  part  of  the  glass  to  the  other,  and 
twirled  about  in  the  air.  Notwithstanding  tin's  ex-] 
plicit  account  of  the  experiment,  it  entirely  failed 
at  the  Royal  Society,  and  the  secretary  was  de- 
sired to  request  the  loan  of  Sir  Isaac's  apparatus,' 
and  to  inquire  whether  or  not  he  had  secured  the 
papers  from  being  moved  by  the  air,  which  might 
have  somewhere  stole  in.  In  a  letter,  dated  21st 
December,  Sir  Isaac  recommended  to  the  society  to 
rub  the  glass  "  with  stuff  whose  threads  may  rake 
its  surface,  and,  if  that  will  not  do,  to  rub  it  with 
the  fingers'  ends  to  and  fro,  and  knock  them  as 
often  upon  the  glass."  These  directions  enabled 
the  society  to  succeed  with  the  experiment  on  the 
13th  January,  1676,  when  they  used  a  scrubbing 
brush  of  short  hog's  bristles,  and  the  heft  of  a  knife 
made  with  whalebone. 

Among  the  minor  inventions  of  Sir  Isaac  Newton, 
we  must  enumerate  his  reflecting  instrument  for 
observing  the  moon's  distance  from  the  fixed  stars 
at  sea.  The  description  of  this  instrument  was  com- 
municated to  Dr.  Halley  in  the  year  1700 ;  but,  either 
from  having  mislaid  the  manuscript,  or  from  attach- 
ing no  value  to  the  invention,  he  never  communi- 
cated it  to  the  Royal  Society,  and  it  remained  among 
his  papers  till  after  his  death  in  1742,  when  it  was 
published  in  the  Philosophical  Transactions.  The 
following  is  Sir  Isaac's  own  description  of  it  as 
communicated  to  Dr.  Halley. 

"  In  the  annexed  figure  PQRS  denotes  a  plate  of 
brass,  accurately  divided  in  the  limb  DQ,  into  J  de- 
grees, i  minutes,  and  ~  minutes,  by  a  diagonal 
scale ;  and  the  i  degrees,  and  £  minutes,  and  -~ 
minutes,  counted  for  degrees,  minutes,  and  j  minutes. 
AB  is  a  telescope  three  or  four  feet  long,  fixed  on 
the  edge  of  that  brass  plate.  G  is  a  speculum  fixed 


276 


SIR   ISAAC   NEWTON. 


on  the  brass   plate   perpendicularly  as    near    as 
may  be  to  the  object-glass  of  the  telescope,  so  as 

Fig.  12. 


to  be  inclined  forty-five  degrees  to  the  axis  of 
the  telescope,  and  intercept  half  the  light  which 
would  otherwise  come  through  the  telescope  to  the 
eye.  CD  is  a  moveable  index  turning  about  the 
centre  C,  and,  with  its  fiducial  edge,  showing  the 
degrees,  minutes,  and  %  minutes  on  the  limb  of  the 
brass  plate  PQ ;  the  centre  C  must  be  over  against 
the  middle  of  the  speculum  G.  H  is  another  specu- 
lum, parallel  to  the  former,  when  the  fiducial  edge 
of  index  falls  on  0°  0'  0" ;  so  that  the  same  star  may 
then  appear  through  the  telescope  in  one  and  the 
same  place,  both  by  the  direct  rays  and  by  the  re- 
flexed  ones ;  but  if  the  index  be  turned,  the  star  shall 
appear  in  two  places,  whose  distance  is  showed  on 
the  brass  limb  by  the  index. 

"By  this  instrument  the  distance  of  the  moon 
from  any  fixed  star  is  thus  observed :  view  the  star 


REFLECTING   MICROSCOPE.  277 

through  the  perspicil  by  the  direct  light,  and  the 
moon  by  the  reflexed  (or  on  the  contrary);  and 
turn  the  index  till  the  star  touch  the  limb  of  the 
moon,  and  the  index  shall  show  on  the  brass  limb 
of  the  instrument  the  distance  of  the  star  from  the 
moon's  limb ;  and  though  the  instrument  shake  by 
the  motion  of  the  ship  at  sea,  yet  the  moon  and  star 
will  move  together  as  if  they  did  really  touch  one 
another  in  the  heavens ;  so  that  an  observation  may 
be  made  as  exactly  at  sea  as  at  land. 

"  And  by  the  same  instrument  may  be  observed 
exactly  the  altitudes  of  the  moon  and  stars,  by 
bringing  them  to  the  horizon ;  and  thereby  the  lati- 
tude and  times  of  observation  may  be  determined 
more  exactly  than  by  the  ways  now  in  use. 

"  In  the  time  of  the  observation,  if  the  instrument 
move  angularly  about  the  axis  of  the  telescope,  the 
star  will  move  in  a  tangent  of  the  moon's  limb,  or 
of  the  horizon ;  but  the  observation  may  notwith- 
standing be  made  exactly,  by  noting  when  the  line 
described  by  the  star  is  a  tangent  to  the  moon's 
limb,  or  to  the  horizon. 

"To  make  the  instrument  useful,  the  telescope 
ought  to  take  in  a  large  angle ;  and  to  make  the 
observation  true,  let  the  star  touch  the  moon's  limb, 
not  on  the  outside,  but  on  the  inside." 

This  ingenious  contrivance  is  obviously  the  very 
same  invention  as  that  which  Mr.  Hadley  produced 
in  1731,  and  which,  under  the  name  oif  Hadley's 
Quadrant,  has  been  of  so  great  service  in  navigation. 
The  merit  of  its  first  invention  must  therefore  be 
transferred  to  Sir  Isaac  Newton. 

In  the  year  1672,  Sir  Isaac  communicated  to 
Mr.  Oldenburg  his  design  for  a  microscope,  which 
he  considered  to  be  as  capable  of  improvement  as 
the  telescope,  and  perhaps  more  so,  because  it 
requires  only  one  speculum.  This  microscope  is 
shown  in  the  annexed  diagram,  where  AB  is  the 
object-metal,  CD  the  eye-glass,  F  their  common 
Aa 


278  SIR   ISAAC    NEWTON. 

focus,  and  0  the  other  focus  of  the  metal  in  which 
the  object  is  placed.    This  ingenious  idea  has  been 

Fig.  13. 


greatly  improved  in  modern  times  by  Professor 
Amici,  who  makes  AB  a  portion  of  an  ellipsoid, 
whose  foci  are  O  and  F,  and  who  places  a  small 
plain  speculum  between  O  and  AB,  in  order  to  re- 
flect the  object,  which  is  placed  on  one  side  AP,  for 
the  purpose  of  being  illuminated. 

In  another  letter  to  Mr.  Oldenburg,  dated  July 
llth  in  the  same  year,  he  suggests  another  improve- 
ment in  microscopes,  which  is  to  "illuminate  the 
object  in  a  darkened  room  with  the  light  of  any 
convenient  colour  not  too  much  compounded :  for 
by  that  means  the  microscope  will,  with  distinct- 
ness, bear  a  deeper  charge  and  larger  aperture, 
especially  if  its  construction  be  such  as  I  may  here- 
after describe."*  This  happy  idea  I  have  some 
years  ago  succeeded  in  realizing,  by  illuminating 
microscopic  objects  with  the  light  of  a  monochro- 
matic lamp,  which  discharges  a  copious  flame  of 
pure  yellow  light  of  definite  refrangibility.f 

In  order  to  remedy  the  evils  arising  from  the 
weak  reflecting  power  of  speculum  metal,  and  from 
its  tarnishing  by  exposure  to  the  air,  Sir  Isaac  pro- 
posed to  substitute  for  the  small  oval  speculum  a 
triangular  prism  of  glass  or  crystal  ABC.  Its  side 

*  Sir  Isaac  does  not  seem  to  have  afterward  described  this  construe 
tion. 

t  See  Edinburgh  Transactions,  vol.  ix.  p.  433,  and  the  Edinburgh 
Journal  of  Science,  July,  1829,  No.  I.  New  Series,  p.  108. 


PRISMATIC   REFLECTOR. 


279 


AB  fa  he  supposes  to  perform  the  office  of  that  metal, 
by  reflecting  towards  the  eye-glass  the  light  which 
comes  from  the  concave  speculum  DF,  fig.  13, 
whose  light  he  supposes  to  enter  into  this  prism  at 
its  side  CB  be,  and  lest  any  colours  should  be  pro^ 
duced  by  the  refraction  of  these  planes,  it  is  requisite 
that  the  angles  of  the 
prism  at  Aa  and  B&  be 
precisely  equal.  This 
maybe  done  most  conve- 
niently, by  making  them 
half  right  angles,  and  con- 
sequently the  third  angle 
at  Cc  a  right  one.  The 
plane  AB  la  will  reflect 
all  the  light  incident  upon 
it ;  but  in  order  to  ex- 
clude unnecessary  light, 
it  will  be  proper  to  cover 
it  all  over  with  some  black  substance  excepting  two 
circular  spaces  of  the  planes  -Ac  and  Be,  through 
which  the  useful  light  may  pass.  The  length  of  the, 

Fig.  15 


prism  should  be  such  that  its 
be  square,  and  so  much  of  the 


Ac  and  Be  may 
B  and  b  as  are 


SIR   ISAAC   NEWTON. 

superfluous  ought  to  be  ground  off,  to  give  passage 
for  as  much  light  as  is  possible  from  the  object  to 
the  speculum. 

One  great  advantage  of  this  prism,  which  cannot 
be  obtained  from  the  oval  metal,  is,  that  without 
using  two  glasses  the  object  may  be  erected,  and 
the  magnifying  power  of  the  telescope  varied  at 
pleasure,  by  merely  varying  the  distances  of  the 
speculum,  the  prism,  and  the  eye-glass.  This  will 
be  understood  from  Jig.  16,  where  AI  represents 

Fig.  16. 


the  great  concave  speculum,  EF  the  eye-glass,  and 
BCD  the  prism  of  glass,  whose  sides  BC  and  CD 
are  not  flat,  but  spherically  convex.  The  rays  which 
come  from  G,  the  focus  of  the  great  speculum  AI, 
will,  by  the  refraction  of  the  first  side  BC,  be  re- 
duced to  parallelism,  and  after  reflection  from  the 
base  CD,  will  be  made  by  the  refraction  of  the  next 
side  BD  to  converge  to  the  focus  H  of  the  eye-glass 
EF.  If  we  now  bring  the  prism  BCD  nearer  the 
image  at  G,  the  point  H  will  recede  from  BD,  and 
the  image  formed  there  will  be  greater  than  that  at 
G,  and  if  we  remove  the  prism  BCD  from  G,  the 
point  H  will  approach  to  BD,  and  the  image  at  H 


IMPRESSIONS    ON    THE    RETINA. 

will  be  less  than  that  at  G.    The  prism  BCD  per- 
forms the  same  part  as  a  convex  lens,  G  and  H 
being  its  conjugate  foci,  and  the  relative  size  of  the 
images  formed  at  these  points  being  proportional  to 
their  distance  from  the  lens.      This  construction 
would  be  a  good  one  for  varying  optically  the  angu- 
lar distance  of  a  pair  of  wires  placed  in  the  focus  of 
.  the  eye-glass  EF ;  and  by  bisecting  the  lenticular 
,  prism  BCD,  and  giving  the  halves  a  slight  inclina- 
;  tion,  we  should  be  able  to  separate  and  to  close  the 
two  images  or  disks  which  would  thus  be  produced, 
and  thus -form  a  double  image  micrometer. 

Among  the  minor  and  detached  labours  of  Sir 
Isaac,  we  must  not  omit  his  curious  experiments  on 
the  action  of  light  upon  the  retina.  Locke  seems 
to  have  wished  his  opinion  respecting  a  fact  stated 
in  Boyle's  Book  on  Colours,  and  in  a  letter  from 
Cambridge,  dated  June  30th,  1691,  he  communicated 
to  his  friend  the  following  very  remarkable  obser- 
vations made  by  himself. 

"  The  observation  you  mention  in  Mr.  Boyle's 
book  of  colours  I  once  made  upon  myself  with  the 
hazard  of  my  eyes.  The  manner  was  this ;  I  looked 
a  very  little  while  upon  the  sun  in  the  looking-glass 
with  my  right  eye,  and  then  turned  my  eyes  into  a 
dark  corner  of  my  chamber,  and  winked,  to  observe 
the  impression  made,  and  the  circles  of  colours 
which  encompassed  it,  and  how  they  decayed  by 
degrees,  and  at  last  vanished.  This  I  repeated  a 
second  and  a  third  time.  At  the  third  time,  when 
the  phantasm  of  light  and  colours  about  it  were 
almost  vanished,  intending  my  fancy  upon  them  to 
see  their  last  appearance,  I  found,  to  my  amaze- 
ment, that  they  began  to  return,  and  by  little  and 
little  to  become  as  lively  and  vivid  as  when  I  had 
newly  looked  upon  the  sun.  But  when  I  ceased  to 
intend  my  fancy  upon  them,  they  vanished  again. 
After  this,  I  found,  that  as  often  as  I  went  into  the 
dark,  and  intended  my  mind  upon  them,  as  wheo 
Aa2 


282  SIR   ISAAC   NEWTON.      JR 

a  man  lobks  earnestly  to  see  any  thing  which  is 
difficult  to  be  seen,  I  could  make  the  phantasm  re- 
turn without  looking  any  more  upon  the  sun ;  and 
the  oftener  I  made  it  return,  the  more  easily  I  could 
make  it  return  again.  And  at  length,  by  repeating 
this  without  looking  any  more  upon  the  sun,  I  made 
such  an  impression  on  my  eye,  that,  if  I  looked  upon 
the  clouds,  or  a  book,  or  any  bright  object,  I  saw 
upon  it  a  round  bright  spot  of  light  like  the  sun, 
and,  which  is  still  stranger,  though  I  looked  upon 
the  sun  with  my  right  eye  only,  and  not  with  my. 
left,  yet  my  fancy  began  to  make  an  impression, 
upon  my  left  eye,  as  well  as  upon  my  right.  For  if 
I  shut  my  right  eye,  or  looked  upon  a  book  or  the 
clouds  with  my  left  eye,  I  could  see  the  spectrum 
of  the  sun  almost  as  plain  as  with  my  right  eye,  if  I 
did  but  intend  my  fancy  a  little  while  upon  it ;  for 
at  first,  if  I  shut  my  right  eye,  and  looked  with  my 
left,  the  spectrum  o'f  the  sun  did  not  appear  till  I  in- 
tended my  fancy  upon  it ;  but  by  repeating,  this  ap- 
peared every  time  more  easily.  And  now,  in  a  few 
hours'  time,  I  had  brought  my  eyes  to  such  a  pass, 
that  I  could  look  upon  no  bright  object  with  either 
eye  but  I  saw  the  sun  before  me,  so  that  I  durst 
neither  write  nor  read ;  but  to  recover  the  use  of  my 
eyes,  shut  myself  up  in  my  chamber  made  dark,  for 
three  days  together,  and  used  all  means  to  divert 
my  imagination  from  the  sun.  For  if  I  thought 
upon  him,  I  presently  saw  his  picture,  though  I  was 
in  the  dark.  But  by  keeping  in  the  dark,  and  em- 
ploying my  mind  about  other  things,  I  began  in 
three  or  four  days  to  have  some  use  of  my  eyes 
again ;  and,  by  forbearing  to  look  upon  bright  ob- 
jects, recovered  them  pretty  well,  though  not  so 
well  but  that,  for  some  months  after,  the  spectrum 
Df  the  sun  began  to  return  as  often  as  I  began  to 
meditate  upon  tha  phenomena,  even  though  I  lay  in 
bed  at  midnight  with  my  curtains  drawn.  But  now( 
I  have  been  very  well  for  many  years,  though  I  am 


IMPRESSIONS    ON   THE    RETINA.  283 

apt  to  think,  if  I  durst  venture  my  eyes,  I  could  still 
make  the  phantasm  return  by  the  power  of  my 
fancy.  This  story  I  tell  you,  to  let  you  understand, 
that  in  the  observation  related  by  Mr.  Boyle,  the 
man's  fancy  probably  concurred  with  the  impression 
made  by  the  sun's  light  to. produce  that  phantasm 
of  the  sun  which  he  constantly  saw  in  bright  objects. 
And  so  your  question  about»the  cause  of  this  phan- 
tasm involves  another  about  the  power  of  fancy, 
which  I  must  confess  is  too  hard  a  knot  for  me  to 
untie.  To  place  this  effect  in  a  constant  motion  is 
hard,  because  the  sun  ought  then  to  appear  per- 
petually. It  seems  rather  to  consist  in  a  disposition 
of  the  sensorium  to  move  the  imagination  strongly, 
and  to  be  easily  moved,  both  by  the  imagination 
and  by  the  light,  as  often  as  bright  objects  are  looked 
upon." 

These  observations  possess  in  many  respects  a  high 
degree  of  interest.  The  fact  of  the  transmission 
of  the  impression  from  the  retina  of  the  one  eye  to 
that  of  the  other  is  particularly  important ;  and  it 
deserves  to  be  remarked,  as  a  singular  coincidence, 
that  I  had  occasion  to  observe  and  to  describe  the 
same  phenomena  above  twenty  years  ago,*  and  long 
oefore  the  observations  of  Sir  Isaac  were  commu- 
nicated to  the  scientific  world. 

*  Art.  Accidental  Colour*  in  the  Edinburgh  Encyclopedia. 


284  SIR   ISAAC   NEWTON 


CHAPTER  XVIII. 

His  Acquaintance,  with  Dr.  Pemberton,  who  edits  the  Third  Edition  of 
the  Principia— His  Jirst  Attack  of  ill  Health— His  Recovery-  He  is 
taken  ill  in  consequence  of  attending  the  Royal  Society — His  Death 
on  the  20th  March,  1727— His  Body  lies  in  state— His  Funeral—He 
is.  buried  in  Westminster  Abbey — His  Monument  described— His  Epi- 
taph— A  Medal  struck  in  honour  of  him — Roubiliac's  full-length 
Statue  of  him  erected  in  Cambridge — Division  of  his  Property — His 
Successors. 

ABOUT  the  year  1722,  Sir  Isaac  was  desirous  of 
publishing  a  third  edition  of  his  Principia,  and  the 
premature  death  of  Mr.  Cotes  having  deprived  him 
of  his  valuable  aid,  he  had  the  good  fortune  to  be- 
come acquainted  with  Dr.  Henry  Pemberton,  a  young 
and  accomplished  physician,  who  had  cultivated 
mathematical  learning  with  considerable  success. 
M.  Poleni,  an  eminent  professor  in  the  University 
of  Padua,  having  endeavoured,  on  the  authority  of 
a  new  experiment,  to  overturn  the  common  opinion 
respecting  the  force  of  bodies  in  motion,  and  to  es- 
tablish that  of  Leibnitz  in  its  place,  Dr.  Pemberton 
transmitted  to  Dr.  Mead  a  demonstration  of  its 
inaccuracy.  Dr.  Mead  communicated  this  paper  to 
Sir  Isaac,  who  not  only  highly  approved  of  it,  but 
added  a  demonstration  of  his  own,  drawn  from 
another  consideration  of  the  subject ;  and  this  was 
printed  without  his  name,  as  a  postscript  to  Pem- 
berton's  paper,  when  it  appeared  in  the  Transac- 
tions.* 

In  a  short  time  after  the  commencement  of  their 
acquaintance,  Sir  Isaac  engaged  Dr.  Pemberton  to 
superintend  the  new  edition  of  the  Principia.  In 
discharging  this  duty,  Dr.  Pemberton  had  occasion 
to  make  many  remarks  on  this  work,  which  Sir  Isaac 

*  Bee  Phil.  Trans.  1722,  vol.  xxxiii.  p.  57. 


ILL   HEALTH.  285 

always  received  with  the  utmost  goodness,  and  the 
new  edition  appeared  with  numerous  alterations  in 
1726.  On  the  occasions  upon  which  he  had  per- 
sonal intercourse  with  Sir  Isaac,  and  which  were 
necessarily  numerous,  he  endeavoured  to  learn  his 
opinions  on  various  mathematical  subjects,  and  to 
obtain  some  historical  information  respecting  his 
inventions  and  discoveries.  Sir  Isaac  entered  freely 
into  all  these  topics ;  and  during  the  conversations 
which  took  place,  and  while  they  were  reading 
together  Dr.  Pemberton's  popular  account  of  Sir 
Isaac's  discoveries,  he  obtained  the  most  perfect 
evidence  that,  though  his  memory  was  much  de- 
cayed, yet  he  was  fully  able  to  understand  his  own 
writings. 

During  the  last  twenty  years  of  his  life,  which  he 
spent  in  London,  the  charge  of  his  domestic  con- 
cerns devolved  upon  his  beautiful  and  accomplished 
niece,  Mrs.  Catharine  Barton,  the  wife  of  Colonel 
Barton,  for  whom,  as  we  have  already  seen,  the 
Earl  of  Halifax  had  conceived  the  warmest  affec- 
tion. This  lady,  who  had  been  educated  at  her 
uncle's  expense,  married  Mr.  Conduit,  and  continued 
to  reside  with  her  husband  in  Sir  Isaac's  house  till 
the  time  of  his  death. 

In  the  year  1722,  when  he  had  reached  the 
eightieth  year  of  his  age,  he  was  seized  with  an 
incontinence  of  urine,  which  was  ascribed  to  stone 
in  the  bladder,  and  was  considered  incurable.  By 
means  of  a  strict  regimen,  however,  and  other  pre- 
cautions, he  was  enabled  to  alleviate  his  complaint, 
and  to  procure  long  intervals  of  ease.  At  this  time 
he  gave  up  the  use  of  his  carriage,  and  always  went 
out  in  a  chair.  He  declined  all  invitations  to  dinner, 
and  at  his  own  house  he  had  only  small  parties.  In 
his  diet  he  was  extremely  temperate.  Though  he 
took  a  little  butcher  meat,  yet  the  principal  articles 
of  his  food  were  broth,  vegetables,  and  fruit,  of 
which  he  always  ate  very  heartily.  In  spite  of  all 


286  SHI   ISAAC   NEWTON. 

his  precautions,  however,  he  experienced  a  return 
of  his  old  complaint,  and  in  August,  1724,  he  passed 
a  stone  the  size  of  a  pea,  which  came  away  in  two 
pieces,  the  one  at  the  distance  of  two  days  from  the 
other.  After  some  months  of  tolerable  good  health, 
he  was  seized  in  January,  1725,  with  a  violent  cough 
and  inflammation  of  the  lungs  ;  and  in  consequence 
of  this  attack,  he  was  prevailed  upon,  with  some 
difficulty,  to  take  up  his  residence  at  Kensington, 
where  his  health  experienced  a  decided  improve- 
ment. In  February,  1725,  he  was  attacked  in  both 
his  feet  with  a  fit  of  the  gout,  of  which  he  had  re- 
ceived a  slight  warning  a  few  years  before,  and  the 
effect  of  this  new  complaint  was  to  produce  a  great 
and  beneficial  change  in  his  general  health.  On 
Sunday  the  7th  March,  when  his  head  was  clearer 
and  his  memory  stronger  than  Mr.  Conduit  had 
known  it  to  be  for  some  time,  he  entered  into  a  long 
conversation  on  various  subjects  in  astronomy.  He 
explained  to  Mr.  Conduit  how  comets  might  be 
formed  out  of  the  light  of  vapours  discharged  from 
the  sun  and  the  fixed  stars  as  the  centres  of  sys- 
tems. He  conceived  that  these  luminaries  were 
replenished  by  the  same  comets  being  again  returned 
to  them ;  and  upon  this  principle  he  explained  the 
extraordinary  lights  which  were  seen  among  the 
fixed  stars  by  Hipparchus,  Tycho  Brahe,  and  Kepler's 
disciples,  and  which  he  supposed  to  arise  from  the 
additional  fuel  which  they  received.* 

Notwithstanding  the  improvement  which  his  health 
had  experienced,  his  indisposition  was  still  suffi- 
ciently severe  to  unfit  him  for  the  discharge  of  his 
duties  at  the  mint ;  and  as  his  old  deputy  was  con- 
fined with  the  dropsy,  he  was  desirous  in  1725  of 
resigning  his  office  to  Mr.  Conduit.  Difficulties 
probably  were  experienced  in  making  this  arrange- 
ment, but  his  nephew  discharged  for  him  all  the 

*  This  conversation,  originally  copied  from  Mr.  Conduit's  handwriting, 
Ui  given  in  the  Appendix,  No.  iii.  p.  320. 


DEATH.  287 

duties  of  his  office ;  and  during  the  last  year  of  his 
life  he  hardly  ever  went  to  the  mint. 

But  though  every  kind  of  motion  was  calculated 
to  aggravate  his  complaint,  and  though  he  had  de- 
rived from  absolute  rest  and  from  the  air  at  Ken- 
sington the  highest  benefit,  yet  great  difficulty  was 
experienced  in  preventing  him  from  occasionally 
going  to  town.  Feeling  himself  able  for  the  jour- 
ney, he  went  to  London  on  Tuesday  the  28th  of 
February,  1727,  to  preside  at  a  meeting  of  the  Royal 
Society.  On  the  following  day  Mr.  Conduit  con- 
sidered him  better  than  he  had  been  for  many  years, 
and  Sir  Isaac  was  himself  so  sensible  of  this  im- 
provement in  his  health,  that  he  assured  his  nephew 
that  on  the  Sunday  preceding,  he  had  slept  from 
eleven  o'clock  at  night  till  eight  o'clock  next  morn- 
ing without  waking.  He  had  undergone,  however, 
great  fatigue  in  attending  the  meeting  of  the  Royal 
Society,  and  in  paying  and  receiving  visits,  and  the 
consequence  of  this  was  a  violent  return  of  his 
former  complaint.  He  returned  to  Kensington  on 
Saturday  the  4th  March,  and  was  attended  by  Dr. 
Mead  and  Dr.  Cheselden,  who  pronounced  his  dis- 
ease to  be  stone,  and  held  out  no  hopes  of  his 
recovery.  From  the  time  of  his  last  journey  to 
London  he  had  experienced  violent  fits  of  pain  with 
very  short  intermissions ;  and  though  the  drops  of 
sweat  ran  down  his  face  during  these  severe  parox- 
ysms, yet  he  never  uttered  a  cry  or  a  complaint,  or 
displayed  the  least  marks  of  peevishness  or  impa- 
tience ;  but  during  the  short  intervals  of  relief  which 
occurred,  he  smiled  and  conversed  with  his  usual 
gayety  and  cheerfulness.  On  Wednesday  the  15th 
of  March  he  seemed  a  little  better;  and  slight, 
though  groundless  hopes  were  entertained  of  his 
recovery.  On  the  morning  of  Saturday  the  18th 
he  read  the  newspapers,  and  carried  on  a  pretty  long 
conversation  with  Dr.  Mead,  when  all  his  senses  and 
faculties  were  strong  and  vigorous ;  but  at  six  o'clock 

1 1  \  i  i  in  I  in  i  m 


288  SIR   ISAAC   NEWTON. 

of  the  same  evening  he  became  insensible,  and  he 
continued  in  that  state  during  the  whole  of  Sunday, 
and  till  Monday  the  20th,  when  he  expired  between 
one  and  two  o'clock  in  the  morning,  in  the  eighty- 
fifth  year  of  his  age. 

His  body  was  removed  from  Kensington  to  Lon- 
don, and  on  Tuesday  the  L8th  March  it  lay  in  state 
in  the  Jerusalem  Chamber,  and  was  thence  conveyed 
to  Westminster  Abbey,  where  it  was  buried  near  the 
entrance  into  the  choir  on  the  left-hand.  The  pall 
was  supported  by  the  Lord  High  Chancellor,  the 
Dukes  of  Roxburghe  and  Montrose,  and  the  Earls 
of  Pembroke,  Sussex,  and  Macclesfield,  who  were 
Fellows  of  the  Royal  Society.  The  Hon.  Sir  Mi- 
chael Newton,  Knight  of  the  Bath,  was  chief 
mourner,  and  was  followed  by  some  other  relations, 
and  several  distinguished  characters  who  were  inti- 
mately acquainted  with  the  deceased.  The  funeral 
service  was  performed  by  the  Bishop  of  Rochester, 
attended  by  the  prebend  and  choir. 

Sensible  of  the  high  honour  which  they  derived 
from  their  connexion  with  so  distinguished  a  phi- 
losopher, the  relations  of  Sir  Isaac  Newton  who 
inherited  his  personal  estate,*  agreed  to  devote  500/« 
to  the  erection  of  a  monument  to  his  memory,  and 
the  dean  and  chapter  of  Westminster  appropriated 
for  it  a  place  in  the  most  conspicuous  part  of  the 
Abbey,  which  had  often  been  refused  to  the  greatest 
of  our  nobility.  This  monument  was  erected  in 
1731.  On  the  front  of  a  sarcophagus  resting  on  a 
pedestal  are  sculptured  in  basso-relievo  youths  bear- 
ing in  their  hands  the  emblems  of  Sir  Isaac's  prin- 
cipal discoveries.  One  carries  a  prism,  another  a 
reflecting  telescope,  a  third  is  weighing  the  sun  and 

*  These  were  the  three  children  of  his  half-brother  Smith,  the  three 
children  of  his  half-sister  Pilkington,  and  the  two  daughters  of  his  half- 
sister  Barton,  all  of  whom  survived  Sir  Isaac.  New  Anecdotes  of  Sir 
Isaac  Newton,  by  J.  H.,  a  Gentleman  of  his  Mother's  Family.  See  An 
nual  Register,  1776,  vol.  xix.  p.  25  of  Characters,  The  author  of  thia 
paper  was  James  Hutton,  Esq.  of  Pimlico. 

?   f  •  !!  ;  {  I  >          • 


MONUMENT.  289 

planets  with  a  steelyard,  a  fourth  is  employed  about 
a  furnace,  and  two  others  are  loaded  with  money 
newly  coined.  On  the  sarcophagus  is  placed  the 
figure  of  Sir  Isaac  in  a  cumbent  posture,  with  his 
elbow  resting  on  several  of  his  works.  Two  youths 
stand  before  him  with  a  scroll,  on  which  is  drawn  a 
remarkable  diagram  relative  to  the  solar  system,  and 
above  that  is  a  converging  series.  Behind  the  sar- 
cophagus is  a  pyramid,  from  the  middle  of  which 
rises  a  globe  in  mezzo-relievo,  upon  which  several 
of  the  constellations  are  drawn,  in  order  to  show 
the  path  of  the  comet  of  1681,  whose  period  Sir 
Isaac  had  determined,  and  also  the  position  of  the 
solstitial  colure  mentioned  by  Hipparchus,  and  by 
means  of  which  Sir  Isaac  had,  in  his  Chronology, 
fixed  the  time  of  the  Argonautic  expedition.  A  figure 
of 'Astronomy  as  Queen  of  the  Sciences  sits  weep- 
ing on  the  Globe  with  a  sceptre  in  her  hand,  and  a 
star  surmounts  the  summit  of  the  pyramid.  The 
following  epitaph  is  inscribed  on  the  monument. 

Hie  situs  est 

Isaacus  Newton,  Eques  Auratus, 

Qui  Animi  Vi  prope  divina, 

Planetarum  Motus,  Figuras, 

Cometarum  Semitas,  Oceanique  JEstus, 

Sua  Mathesi  facem  preferente, 

Primus  demon stravit. 

Radiorum  Lucis  dissimilitudines, 

Colorumque  inde  nasceniium  Proprietates, 

Quas  nemo  aniea  vel  suspicatus  erat,  pervestigavit, 

Naturae,  Antiquitates,  S.  Scriptures, 

Sedulus,  sagax,  fidus  Interpres, 
Dei  Opt.  Max.  Majestatem  Philosophia  asseruit, 

Evangelii  simplicitatem  moribus  expressit. 
Sibi  gratulentur  Mortales,  tale  tantumque  extitisse, 

HUMANI  GENERIS  DECUS. 

Natus  xxv.  Decemb.  MDCXL1I.  Obiit.  xx.  Mar. 

MDCCXXVII. 

Of  which  the  following  is  a  literal  translation : 

Here  lies 

••  Isaac  Newton,  Knight, 
Who,  by  a  Vigour  of  Mind  almost  supernatural, 

First  demonstrated 
The  Morions  and  Figures  of  the  Planets, 

Bb 


290  SIR  ISAAC 

The  Paths  of  the  Comets,  and  the  Tides  of  the  Ocean 

He  diligently  investigated 

The  different  Re  fr  eligibilities  of  the  Rays  of  Light, 

And  the  Properties  of  the  Colours  to  which  they  give  rise. 

AM  assiduous,  sagacious,  and  faithful  Interpreter 

Of  Nature,  Antiquity,  and  the  Holy  Scriptures, 

He  asserted  in  his  Philosophy  the  Majesty  of  God, 

And  exhibited  in  his  conduct  the  Simplicity  of  the  Gospel. 

Let  Mortals  rejoice 
That  there  has  existed  such  and  so  great 

AN  OKNAMENT  op-  HFMAN  NATTHE. 
Born  25th  Dec.  1642,  Died  20th  March,  1727. 

In  the  beginning  of  1731,  a  medal  was  struck 'at 
the  Tower  in  honour  of  Sir  Isaac  Newton.  It  had 
on  one  side  the  head  of  the  philosopher,  with  the 
motto,  Felix  cognoscere  causas,  and  on  the  reverse  a 
figure  representing  the  mathematics. 

On  the  4th  February,  1755,  a  magnificent  full- 
length  statue  of  Sir  Isaac  Newton  in  white  marble 
was  erected  in  the  antechapel  of  Trinity  College. 
He  is  represented  standing  on  a  pedestal  in  a  loose 
gown,  holding  a  prism,  and  looking  upwards  with  an 
expression  of  the  deepest  thought.  On  the  pedestal 
is  the  inscription, 

Qui  genus  humanum  ingenio  superavit. 
Who  surpassed  all  men  in  genius. 

This  statue,  executed  by  Roubiliac,  was  erected 
at  the  expense  of  Dr.  Robert  Smith,  the  author  of 
the  Compleat  System  of  Optics,  and  professor  of  as- 
tronomy and  experimental  philosophy  at  Cambridge. 
— It  has  been  thus  described  by  a  modern  poet : 

Hark  where  the  organ,  full  and  clear, 
With  loud  hosannas  charms  the  ear; 
Behold,  a  prism  within  his  hands, 
Absorbed  in  thought  great  Newton  stands 
Such  was  his  brow,  and  looks  serene, 
His  serious  gait  and  musing  mien, 
When  taught  on  eagle  wings  to  fly, 
He  traced  the  wonders  of  the  sky ; 
The  chambers  of  the  sun  explored, 
Where  tints  of  thousand  hues  were  stored. 

pr.  Smith  likewise  bequeathed  the  sum  of  500/. 


PROPERTY SUCCESSORS.  291 

for  executing  a  painting  on  glass  for  the  window  at 
the  south  end  of  Trinity  College,  Cambridge.  The 
subject  represents  the  presentation  of  Sir  Isaac 
Newton  to  his  majesty  George  III.,  who  is  seated 
under  a  canopy  with  a  laurel  chaplet  in  his  hand,  and 
attended  by  the  British  Minerva,  apparently  advising 
him  to  reward  merit  in  the  person  of  the  great  phi- 
losopher. Below  the  throne,  the  Lord  Chancellor 
Bacon  is  proposing  to  register  the  reward  about  to 
be  conferred  upon  Sir  Isaac.  The  original  drawing 
of  this  absurd  picture  was  executed  by  Cypriani, 
and  cost  one  hundred  guineas. 

The  personal  estate  of  Sir  Isaac  Newton,  which 
was  worth  about  32,000/.,  was  divided  among  his 
four  nephews  and  four  nieces  of  the  half-blood,  the 
grandchildren  of  his  mother  by  the  Reverend  Mr. 
Smith.  The  family  estates  of  Woolsthorpe  and 
Sustern  he  bequeathed  to  John  Newton,  the  heir-at- 
law,  whose  great-grandfather  was  Sir  Isaac's  uncle. 
This  gentleman  does  not  seem  to  have  sufficiently 
valued  the  bequest,  for  he  sold  them  in  1732,  to  Ed- 
mund Turnor  of  Stoke  Rocheford.*  A  short  time 
before  his  death,  Sir  Isaac  gave  away  an  estate  in 
Berkshire  to  the  sons  and  daughter  of  a  brother  of 
Mrs.  Conduit,  who,  in  consequence  of  their  father 
dying  before  Sir  Isaac,  had  no  share  in  the  personal 
estate  ;  and  he  also  gave  an  estate  of  the  same  value, 
which  he  bought  at  Kensington,  to  Catharine,  the 
only  daughter  of  Mr.  Conduit,  who  afterward  mar- 
ried Mr.  Wallop,  the  eldest  son  of  Lord  Lymington. 
This  lady  was  afterward  Viscountess  Lymington, 
and  the  estate  of  Kensington  descended  to  the  late 
Earl  of  Portsmouth,  by  whom  it  was  sold.  Sir  Isaac 
was  succeeded  as  master  and  warden  in  the  mint  by 
his  nephew,  John  Conduit,  Esq.,  who  wrote  a  trea- 
tise on  the  gold  and  silver  coin,  and  who  died  in 
1737,  leaving  behind  him  his  wife  and  daughter,  the 
Dormer  of  whom  died  in  1739,  in  the  59th  year  of 
her  age. 

*  Tunwr's  Collections^  &c.  p.  158.    See  APPENDIX,  P  3J6' 


292  SIR   ISAAC   NEWTON 


CHAPTER  XIX. 

Permanence  of  Newton's  Reputation— Character  of  his  Genius — His 
Methods  of  Investigation  similar  to  that  used  by  Galileo — Error  in 
ascribing  his  Discoveries  to  the  Use  of  the  Methods  recommended  by 
Lord  Bacon — The  Pretensions  of  the  Baconian  Philosophy  examined 
— Sir  Isaac  Newton' s  social  Character— His  great  Modesty— The 
Simplicity  of  his  Character — His  religious  and  moral  Character — 
His  Hospitality  and  Mode  of  Life — His  Generosity  and  Charity — 
His  Absence — His  personal  "Appearance — Statues  and  Pictures  of 
him — Memorials  and  Recollections  of  him. 

SUCH  were  the  last  days  of  Sir  Isaac  Newton,  and 
such  the  last  laurels  which  were  shed  over  his  grave. 
A  century  of  discoveries  has  since  his  day  been 
added  to  science  ;  but  brilliant  as  these  discoveries 
are,  they  have  not  obliterated  the  minutest  of  his 
labours,  and  have  served  only  to  brighten  the  halo 
which  encircles  his  name.  The  achievements  of 
genius,  like  the  source  from  which  they  spring,  are 
indestructible.  Acts  of  legislation  and  deeds  of  war 
may  confer  a  high  celebrity,  but  the  reputation  which 
they  bring  is  only  local  and  transient;  and  while 
they  are  hailed  by  the  nation  which  they  benefit, 
they  are  reprobated  by  the  people  whom  they  ruin? 
or  enslave.  The  labours  of  science,  on  the  contrary, 
bear  along  with  them  no  counterpart  of  evil.  They 
are  the  liberal  bequests  of  great  minds  to  every 
individual  of  their  race,  and  wherever  they  are  wel- 
comed and  honoured  they  become  the  solace  of 
private  life,  and  the  ornament  and  bulwark  of  the 
commonwealth. 

The  importance  of  Sir  Isaac  Newton's  discoveries 
has  been  sufficiently  exhibited  in  the  preceding 
chapters :  the  peculiar  character  of  his  genius,  and 
the  method  which  he  pursued  in  his  inquiries,  can 
be  gathered  only  from  the  study  of  his  works,  and 


CHARACTER    OF   HIS    GENIUS.  293 

From  the  history  of  his  individual  labours.  Were 
we  to  judge  of  the  qualities  of  his  mind  from  the 
early  age  at  which  he  made  his  principal  discoveries, 
and  from  the  rapidity  of  their  succession,  we  should 
^e  led  to  ascribe  to  him  that  quickness  of  penetra- 
tion, and  that  exuberance  of  invention,  which  is 
more  characteristic  of  poetical  than  of  philosophical 
jehius.  But  we  must  recollect  that  Newton  was 
Placed  in  the  most  favourable  circumstances  for  the 
development  of  his  powers.  The  flower  of  his 
youth  and  the  vigour  of  his  manhood  were  entirely 
levoted  to  science.  No  injudicious  guardian  con- 
;rolled  his  ruling  passion,  and  no  ungenial  studies  or 
)rofessional  toils  interrupted  the  continuity  of  his 
mrsuits.  His  discoveries  were,  therefore,  the  fruit 
of  persevering  and  unbroken  study;  and  he  himself 
declared,  that  whatever  service  he  had  done  to  the 
public  was  not  owing  to  any  extraordinary  sagacity, 
)ut  solely  to  industry  and  patient  thought. 

Initiated  early  into  the  abstractions  of  geometry, 
le  was  deeply  imbued  with  her  cautious  spirit ;  and 
f  his  acquisitions  were  not  made  with  the  rapidity 
of  intuition,  they  were  at  least  firmly  secured ;  and 
;he  grasp  which  he  took  of  his  subject  was  propor- 
lonal  to  the  mental  labour  which  it  had  exhausted. 
Overlooking  what  was  trivial,  and  separating  what 
was  extraneous,  he  bore  down  with  instinctive 
sagacity  on  the  prominences  of  his  subject,  and 
laving  thus  grappled  with  its  difficulties,  he  never 
Bailed  to  intrench  himself  in  its  strongholds. 

To  the  highest  powers  of  invention  Newton 
added,  what  so  seldom  accompanies  them,  the  talent 
of  simplifying  and  communicating  his  profoundest 
speculations.*  In  the  economy  of  her  distributions, 
nature  is  seldom  thus  lavish  of  her  intellectual  gifts 
The  inspired  genius  which  creates  is  rarely  eon- 

*  This  valuable  faculty  characterizes  all  his  writings,  whether  theo- 
logical, chymical,  or  mathematical ;  but  it  is  peculiarly  displaced  4fl  hit 
treatise  on  Universal  Arithmetic,  and  in  his  Optical  Lectures. 


294  SIR   ISAAC   NEWTON. 

ferred  along  with  the  matured  judgment  which 
combines,  and  yet  without  the  exertion  of  both  the 
fabric  of  human  wisdom  could  never  have  been 
reared.  Though  a  ray  from  heaven  kindled  the 
vestal  fire,  yet  an  humble  priesthood  was  required  to 
keep  alive  the  flame. 

The  method  of  investigating  truth  by  observation 
and  experiment,  so  successfully  pursued  in  the  Prin- 
cipia,  lias  been  ascribed  by  some  modern  writers  of 
great  celebrity  to  Lord  Bacon  ;  and  Sir  Isaac  New- 
ton is  represented  as  having  owed  all  his  discoveries 
to  the  application  of  the  principles  of  that  distin- 
guished writer.  One  of  the  greatest  admirers  of 
Lord  Bacon  has  gone  so  far  as  to  characterize  him 
as  a  man  who  has  had  no  rival  in  the  times  which 
are  past,  and  as  likely  to  have  none  in  those  which 
are  to  come.  In  a  eulogy  so  overstrained  as  this, 
we  feel  that  the  language  of  panegyric  has  passed 
into  that  of  idolatry ;  and  we  are  desirous  of  weigh- 
ing the  force  of  arguments  which  tend  to  depose 
Newton  from  the  high-priesthood  of  nature,  and  to 
unsettle  the  proud  destinies  of  Copernicus,  Galileo, 
and  Kepler. 

That  Bacon  was  a  man  of  powerful  genius,  and 
endowed  with  varied  and  profound  talent, — the  most 
skilful  logician, — the  most  nervous  and  eloquent 
writer  of  the  age  which  he  adorned,  are  points  which 
have  been  established  by  universal  suffrage.  The 
study  of  ancient  systems  had  early  impressed  him 
with  the  conviction  that  experiment  and  observation 
were  the  only  sure  guides  in  physical  inquiries ; 
and,  ignorant  though  he  was  of  the  methods,  the 
principles,  and  the  details  of  the  mathematical 
sciences,  his  ambition  prompted  him  to  aim  at  the 
construction  of  an  artificial  system  by  which  the 
laws  of  nature  might  be  investigated,  and  which 
might  direct  the  inquiries  of  philosophers  in  every 
future  age.  The  necessity  of  experimental  research, 
and  of  advancing  gradually  from  the  study  of  facts 


BACONIAN   PHILOSOPHY.  295 

,0  the  determination  of  their  cause,  though  the 
5To~undwork  of  Bacon's  method,  is  a  doctrine  which 
was  not  only  inculcated  but  successfully  followed 
Dy  preceding  philosophers.  In  a  letter  from  Tycho 
Brahe  to  Kepler,  this  industrious  astronomer  urges 
us  pupil  "  to  lay  a  solid  foundation  for  his  views 
>y  actual  observation,  and  then  by  ascending  from 
hese  to  strive  to  reach  the  causes  of  things ;"  and 
t  was  no  doubt  under  the  influence  of  this  advice 
hat  Kepler  submitted  his  wildest  fancies  to  the  test 
f  observation,  and  was  conducted  to  his  most 
plendid  discoveries.  The  reasonings  of  Corjejjii-  x 
us,  who  preceded  Bacon  by  more  than  a  century, 
Were  all  founded  upon  the  most  legitimate  induction. 
}r.  Gilbert  had  exhibited  in  his  treatise  on"  the  ; 
agnet*  the  most  perfect  specimen  of  physical  re- 
earch.  Leonardo  da  Vinci  had  described  in  the 
learest  manner  the  proper  method  of  philosophical 
nvestigation  ;f  and  the  whole  scientific  career  of 
Galileo  was  one  continued  example  of  the  most 

*  De  Magnet  e,  p.  42,  52,  169,  and  Pref.  p.  30. 

t  The  following  passages  from  Leonardo  da  Vinci  are  very  striking : 

"  Theory  is  the  general,  and  practice  the  soldiers. 

"  Experiment  is  the  interpreter  of  the  artifices  of  nature.  It  never 
eceives  us  ;  it  is  our  judgment  itself  which  sometimes  deceives  us,  be- 
duse  we  expect  from  it  effects  which  are  contrary  to  experiment.  We 
nust  consult  experiment  by  varying  the  circumstances  till  we  have 
educed  from  it  general  laws ;  for  it  is  it  which  furnishes  true  laws. 

"  In  the  study  of  the  sciences  which  depend  on  mathematics,  those 
rtio  do  not  consult  nature,  but  authors,  are  not  the  children  of  nature ; 
ley  are  only  her  grandchildren.  Nature  alone  is  the  master  of  true 
enius. 

"In  treating  any  particular  subject,  I  would  first  of  all  make  some 
xperiments,  because  my  design  is  first  to  refer  to  experiment,  and  then 

demonstrate  why  bodies  are  constrained  to  act  in  such  a  manner. 

his  is  the  method  which  we  ought  to  follow  in  investigating  the  phe- 

omena  of  nature.     It  is  very  true  that  nature  begins  by  reasoning  and 

nds  with  experiment ;  but  it  matters  not,  we  must  take  the  opposite 

ourse;  as  I  have  said,  we  must  begin  by  experiment,  and  endeavour 

y  its  means  to  discover  general  principles  "    Thus,  says  Ventusi,  spoke 

eonarc!  a  century  before  Bacon,  and  thus,  we  add,  did  Leonard  tell  phi- 

osophers  all  that  they  required  for  the  proper  investigation  of  general 

aws.    See  Essai  sur  Us  ozuvrages  physico-mathematiques  de  Leonard 

de  Vinci,  par  J.  B.  Venturi.    Paris,  1799,  p.  32,  33,  &c.     See  also  Carlo 

Amoretti's  Memorie  storichs  su  la  vita  gli  studi  e  le  Opere  de  Lionardo 

da  Vinci.    Milano,  1804. 


296  SIR    ISAAC   NEWTON. 

sagacious  application  of  observation  and  experiment 
to  the  discovery  of  general  laws.  The  names  of 
Paracelsus,  Van  Helmont,  and  Cardan  have  been 
ranged  in  opposition  to  this  constellation  of  great 
names,  and  while  it  is  admitted  that  even  they  had 
thrown  off  the  yoke  of  the  schools,  and  had"  suc- 
ceeded in  experimental  research,  their  credulity  and 
their  pretensions  have  been  adduced  as  a  proof  that 
to  the  "  bulk  of  philosophers"  the  method  of  induc- 
tion was  unknown.  The  fault  of  this  argument  con- 
sists in  the  conclusion  being  infinitely  more  general 
than  the  fact.  The  errors  of  these  men  were  not. 
founded  on  their  ignorance,  but  on  their  presump- 
tion. They  wanted  the  patience  of  philosophy  and 
not  her  methods.  An  excess  of  vanity,  a  wayward- 
ness of  fancy,  and  an  insatiable  appetite  for  that 
species  of  passing  fame  which  is  derived  from  eccen- 
tricity of  opinion,  moulded  the  reasonings  and  dis- 
figured the  writings  of  these  ingenious  men ;  and  it 
can  scarcely  admit  of  a  doubt,  that,  had  they  lived 
in  the  present  age,  their  philosophical  character 
would  have  received  the  same  impress  from  the 
peculiarity  of  their  tempers  and  dispositions.  This 
is  an  experiment,  however,  which  cannot  now  be 
made ;  but  the  history  of  modern  science  supplies 
the  defect,  and  the  experience  of  every  man  fur- 
nishes a  proof  that  in  the  present  age  there  are 
many  philosophers  of  elevated  talents  and  inventive 
genius  who  are  as  impatient  of  experimental  re- 
search as  Paracelsus,  as  fanciful  as  Cardan,  and  as 
presumptuous  as  Van  Helmont. 

Having  thus  shown  that  the  distinguished  philoso- 
phers who  flourished  before  Bacon  were  perfect 
masters  both  of  the  principles  and  practice  of  in-, 
ductive  research,  it  becomes  interesting  to  inquire 
whether  or  not  the  philosophers  who  succejeded 
him  acknowledged  any  obligation  to  his  system,  or 
derived  the  slightest  advantage  from  his  precepts. 
If  Bacon  constructed  a  method  to  which  modern 


BACONIAN   PHILOSOPHY.  297 

cience  owes  its  existence,  we  shall  find  its  cultiva- 
ars  grateful  for  the  gift,  and  offering  the  richest 
icense  at  the  shrine  of  a  benefactor  whose  gene- 
ous  labours  conducted  them  to  immortality.  No 
uch  testimonies,  however,  are  to  be  found.  Nearly 
wo  hundred  years  have  gone  by,  teeming  with 
le  richest  fruits  of  human  genius,  and  no  grateful 
isciple  has  appeared  to  vindicate  the  rights  of  the 
lleged  legislator  of  science.  Even  Newton,  who 
as  born  and  educated  after  the  publication  of  the 
'ovum  Organon,  never  mentions  the  name  of  Bacon  !| 
r  his  system,  and  the  amiable  and  indefatigable 
oyle  treated  him  with  the  same  disrespectful 
lence.  When  we  are  told,  therefore,  that  Newton 
wed  all  his  discoveries  to  the  method  of  Bacon, 
othing  more  can  be  meant  than  that  he  proceeded 
i  that  path  of  observation  and  experiment  which 
ad  been  so  warmly  recommended  in  the  Novum 
rganon ;  but  it  ought  to  have  been  added,  that  the 
ame  method  was  practised  by  his  predecessors, — 
lat  Newton  possessed  no  secret  that  was  not  used 
y  Galileo  and  Copernicus, — and  that  he  would 
ave  enriched  science  with  the  same  splendid  dis- 
overies  if  the  name  and  the  writings  of  Bacon  had 
ever  been  heard  of. 

From  this  view  of  the  subject  we  shall  now  pro- 

ed  to  examine  the  Baconian  process  itself,  and 

onsider  if  it  possesses  any  merit  as  an  artificial 

lethod  of  discovery,  or  if  it  is  at  all  capable  of  being 

mployed,  for  this  purpose,  even  in  the  humblest 

alks  of  scientific  inquiry. 

The  process  of  Lord  Bacon  was,  we  believe,  never 

ied  by  any  philosopher  but_  himself.     As  the  sub- 

ect  ot  its  application,  he  selected  that  of  heat.   With 

'.s  usual  erudition,  he  collected  all  the  facts  which 

dence  could  supply, — he  arranged  them  in  tables, — • 

e  cross-questioned  them  with  all  the  subtlety  of  a 

pleader, — he  combined  them  with  all  the  sagacity 

f)f  a  judge, — and  he  conjured  with  them  by  all  the 


298  SIR   ISAAC   NEWTON. 

I  magic  of  his  exclusive  processes.  But,  after  all  thi 
display  of  physical  logic,  nature  thus  interrogate* 
was  still  silent.  The  oracle  which  he  had  himsel 
established  refused  to  give  its  responses,  and  th 
ministering  priest  was  driven  with  discomfiture  fron 
his  own  shrine.  This  example,  in  short,  of  the  ap 
plication  of  his  system,  will  remain  to  future  age 
as  a  memorable  instance  of  the  absurdity  of  attempt 
ing  to  fetter  discovery  by  any  artificial  rules. 

Nothing  even  in  mathematical  science  can  b< 
more  certairTthari~tljat  a  collection  of  scientific  fact 
are  of  theniselves^iiicapable  of  leading  to  discover}/ 
or  to  the  determinatioif  or^iieral  Taws,  unless  lifie] 
'conTaTfn:Ke~rpre'Jqniihating  fact  or  relation  in  whicj 
fee  discovery  mainly  resides.  A  vertical  column  o 
arch-stones  possesses  more  strength  than  the  sam 
materials  arranged  in  an  arch  without  the  key-stone 
However  nicely  they  are  adjusted,  and  however  no 
bly  the  arch  may  spring,  it  never  can  possess  eithe 
equilibrium  or  stability.  In  this  comparison  all  th< 
facts  are  supposed  to  be  necessary  to  the  final  re 
suit;  but,  ill  the  inductive  method,  it  is  impossihl< 
to  ascertain  the  relative  importance  of  any  facts,  o 
even  tiyjetermina^ "the Tacts  have  any  value  at  all 
till  the{master-fact^hrcri  constitutes  the  discover 
has  crowned  the  zealous  efforts  of  the  aspiring  phi 
'  losopher.  The  mind  then  returns  to  the  dark  am 
barren  waste  over  which  it  has  been  hovering ;  am 
by  the  guidance  of  this  single  torch  it  embraces 
under  the  comprehensive  grasp  of  general  princi 
pies,  the  multifarious  and  insulated  phenomena  whicl 
had  formerly  neither  value  nor  connexion.  Henc< 
it  must  be  obvious  to  the  most  superficial  thinker 
that  discovery  consists  either  in  the  detection  o: 
some  concealed  relation — some  deep-seated  affinity 
which  baffles  ordinary  research,  or  in  the  discover] 
;of  some  simple  fact  which  is  connected  by  slende 
ramifications  with  the  subject  to  be  investigated 
but  which,  when  once  detected,  carries  us  back  fo 


TRUE    PROCESS    OF   INVESTIGATION.  299 

s  divergence  to  all  the  phenomena  which  it  em- 
races  and  explains. 

In  order  to  give  additional  support  to  these  views, 
would  be  interesting  to  ascertain  the  general  char- 
ter of  the  process  by  which  a  mind  of  acknow- 
dged  power  actually  proceeds  in  the  path  of  suc- 
issful  inquiry.     The  history  of  science  does  not 
urnish  us  with  much  information  on  this  head,  and 
it  is  to  be  found  at  all,  it  must  be  gleaned  from 
lie  biographies  of  eminent  men.     Whatever  this 
rocess  may  be  in  its  details,  if  it  has  any,  there 
annot  be  the  slightest  doubt  that  in  its  generalities 
t  least  it  is  the  very  reverse  of  the  method  of  in- 
uction.     The  impatience  of  genius  spurns  the  re- 
Taints  of  mechanical  rules,  and  never  will  submit 
>  the  plodding  drudgery^, of  inductive  discipline, 
he  discovery  of  a  newHSirtNmfits  even  a  patient 
lind  for  deliberate  inquiry?"  Conscious  of  having 
dded  to  science  what  had  escaped  the  sagacity  of 
Tmer  ages,  the  ambitious  spirit  invests  its  new 
cquisition  with  an  importance  which  does  not  be- 
ng  to  it.     He  imagines  a  thousand  consequences 
i  flow  from  his4iscover$:  he  forms  innumerable 
leories  to  explaiii^itrana  he  exhausts  his  fancy  in 
ying  all  its  possible  relations  to  recognised  diffi- 
alties  and  unexplained  facts.     The  reins,  however, 
ms  freely  given  to  his  imagination,  are  speedily 
rawn  up.     His  wildest  conceptions  are  all  subjected 
the  rigid  test  of  experiment,  and  he  has  thus  been 
urried  by  the  excursions  of  his  own  fancy  into  new 
nd  fertile  paths,  far  removed  from  ordinary  obser- 
,tion.     Here  the  peculiar  character  of  his  own  ge- 
us  displays  itself  by  the  invention  of  methods  of 
ying  his  own  speculations,  and  he  is  thus  often  led 
new  discoveries  far  more  important  and  general 
an  that  by  which  he  began  his  inquiry.     For  a 
nfirmation  of  these  views,  we  may  refei  to  the 
istory  of  Kepler's  Discoveries ;  and  if  we  do  not  j 
recognise  them  to  the  same  extent  hi  the  labours  of 

I 


300  SIR   ISAAC   NEWTON. 

I  Newton,  it  is  because  he  kept  back  his  discoverie! 
till  they  were  nearly  perfected,  and  therefore  with 
1  held  the  successive  steps  of  his  inquiries. 
>,  The  social  character  of  Sir  Isaac  Newton  wa? 
such  as  might  have  been  expected  from  his  intel 
lectual  attainments.  He  was  modest,  candid,  am 
affable,  and  without  any  of  the  eccentricities  of  ge> 
nius,  suiting  himself  to  every  company,  and  speaking 
of  himself  and  others  in  such  a  manner  that  he  wai 
never  even  suspected  of  vanity.  "  But  this,"  says 
Dr.  Pemberton,  "  I  immediately  discovered  in  him 
which  at  once  both  surprised  and  charmed  me* 
Neither  his  extreme  great  age  nor  his  universal  re* 
putation  had  rendered  him  stiff  in  opinion,  or  in  anj 
degree  elated.  Of  this  I  had  occasion  to  ha1** 
almost  daily  experience.  The  remarks  I  continual!) 
sent  him  by  letters  on  the  Principia  were  receivec 
with  the  utmost  goodness.  These  were  so  far  froir 
being  any  ways  displeasing  to  him,  that  on  the  con- 
trary it  occasioned  him  to  speak  many  kind  thing? 
of  me  to  my  friends,  and  to  honour  me  with  a  public 
testimony  of  his  good  opinion." 

The  modesty  of  Sir  Isaac  Newton  in  reference  tc 
his  great  discoveries  was  not  founded  on  any  indif- 
ference to  the  fame  which  they  conferred,  or  upor 
any  erroneous  judgment  of  their  importance  tc 
science.  The  whole  of  his  life  proves,  that  he  kne\\ 
his  place  as  a  philosopher,  and  was  determined  tc 
assert  and  vindicate  his  rights.  His  modesty  arose 
from  the  depth  and  extent  of  his  knowledge,  whicl: 
showed  him  what  a  small  portion  of  nature  he  hac 
been  able  to  examine,  and  how  much  remained  tc 
be  explored  in  the  same  field  in  which  he  had  him- 
'self  laboured.  In  the  magnitude  of  the  comparisor 
he  recognised  his  own  littleness  ;  and  a  short  time 
before  his  death  he  uttered  this  memorable  senti- 
ment : — "  I  do  not  know  what  I  may  appear  to  the 
world ;  but  to  myself  I  seem  to  have  been  only  like 
a  boy  playing  on  the  seashore,  and  diverting  myself 


SIMPLICITY    OF    CHARACTER.  301 

in  now  and  then  fading  a  smoother  pebble  or  a  pret 
tier  shell  than  ordinary,  while  the  great  ocean  of 
truth  lay  all  undiscovered  before  me."  What  a  les- 
son to  the  vanity  and  presumption  of  philosophers, 
— to  those  especially  who  have  never  even  found  the 
smoother  pebble  or  the  prettier  shell !  What  a  pre- 
paration for  the  latest  inquiries,  and  the  last  views 
of  the  decaying  spirit, — for  those  inspired  doctrines 
which  alone  can  throw  a  light  over  the  dark  ocean 
of  undiscovered  truth ! 

The  native  simplicity  of  Sir  Isaac  Newton's  mind 
is  finely  portrayed  in  the  affecting  letter  in  which 
he  acknowledges  to  Locke  that  he  had  thought  and 
spoken  of  him  uncharitably ;  and  the  humility  and 
candour  in  which  he  asks  forgiveness  could  have 
emanated  only  from  a  mind  as  noble  as  it  was  pure. 

In  the  religious  and  moral  character  of  our  author 
there  is  much  to  admire  and  to  imitate.  While  he 
exhibited  in  his  life  and  writings  an  ardent  regard 
for  the  general  interests  of  religion,  he  was  at  the 
same  time  a  firm  believer  in  revelation.  He  was 
too  deeply  versed  in  the  Scriptures,  and  too  much 
imbued  with  their  spirit,  to  judge  harshly  of  other 
men  who  took  different  views  of  them  from  himself. 
He  cherished  the  great  principles  of  religious  tole- 
ration, and  never  scrupled  to  express  his  abhorrence 
persecution,  even  in  its  mildest  form.  Immo- 
rality and  impiety  he  never  permitted  to  pass  unre- 
proved ;  and  when  Dr.  Halley*  ventured  to  say  any 
thing  disrespectful  to  religion,  he  invariably  checked 
him,  and  said,  "  I  have  studied  these  things, — you 
have  not."f 

After  Sir  Isaac  Newton  took  up  his  residence  in 
London,  he  lived  in  a  very  handsome  style,  and  kept 
his  carriage,  with  an  establishment  of  three  male 

*  Mr.  Hearne,  in  a  memorandum  dated  April  4th,  1726,  states,  that  a 
great  quarrel  happened  between  Sir  Isaac  Newton  and  Mr.  Halley.    If 
this  is  true,  the  difference  is  likely  to  have  originated  in  Halley's  impiety. 

*  Professor  Rigaud  of  Oxford  heard  this  anecdote  from  Dr.  Maskelyne 

Cc 


302  SIR   ISAAC    KEWTOX, 

and  three  female  servants-  In  his  own  house  he 
was  hospitable  and  kind,  and  on  proper  occasions 
he  gave  splendid  entertainments,  though  without 
ostentation  or  vanity.  His  own  diet  was  frugal,  and 
his  dress  was  always  simple ;  but  on  one  occasion, 
when  he  opposed  the  Honourable  Mr.  Annesley  in 
1705,  as  a  candidate  for  the  university,  he  is  said  to 
have  put  on  a  suit  of  laced  clothes. 

His  generosity  and  charity  had  no  bounds,  and  he 
used  to  remark,  that  they  who  gave  away  nothing 
till  they  died  never  gave  at  all.  Though  his  wealth 
had  become  considerable  by  a  prudent  economy,  yet 
he  had  always  a  contempt  for  money,  and  he  spent 
a  considerable  part  of  his  income  in  relieving  the 
poor,  in  assisting  his  relations,  and  in  encouraging 
ingenuity  and  learning.  The  sums  which  he  gave 
to  his  relations  at  different  times  were  enormous  ;* 
and  in  1724  he  wrote  a  letter  to  the  Lord  Provost 
of  Edinburgh,  offering  to  contribute  20/.  per  annum 
to  a  provision  for  Mr.  Maclaurin,  provided  he  ac- 
cepted the  situation  of  assistant  to  Mr.  James  Greg- 
ory, who  was  professor  of  mathematics  in  the  uni- 
versity. 

The  habits  of  deep  meditation  which  Sir  Isaac 
Newton  had  acquired,  though  they  did  not  show 
themselves  in  his  intercourse  with  society,  exer- 
cised their  full  influence  over  his  mind  when  in  the 
midst  of  his  own  family.  Absorbed  in  thought  he 
would  often  sit  down  on  his  bedside  after  he  rose, 
and  remain  there  for  hours  without  dressing  himself, 
occupied  with  some  interesting  investigation  which 
had  fixed  his  attention.  Owing  to  the  same  absence 
of  mind,  he  neglected  to  take  the  requisite  quantity 

*  "  He  was  very  kind  to  all  the  Ayscoughs.  To  one  h«  gave  8007.,  U» 
another  2001,  and  to  a  third  100/.,  and  many  other  sums  ;  and  other  en 
gagemems  did  he  enter  into  also  for  them.  He  was  the  ready  assistant 
of  all  who  were  any  way  related  to  him, — to  their  children  and  grandchil- 
dren."— Annual  Register,  1776,  vol.  xix.  p.  25.  Sir  Isaac  gave  some  do* 
nations  to  the  chapel  and  parish  of  Colstenvorth.  Hearne  says  "  that 
he  promised  to  become  a  benefactor  to  the  Royal  Society,  but  failed  " 


PERSONAL  APPEARANCE.          303* 

oi  nourishment,  and  it  was  therefore  often  necessary 
to  remind  him  of  his  meals.* 

Sir  Isaac  Newton  is  supposed  to  have  had  little 
knowledge  of  the  world,  and  to  have  been  very  ig- 
norant of  the  habits  of  society.  This  opinion  has, 
we  think,  been  rashly  deduced  from  a  letter  which 
he  wrote  in  the  twenty-seventh  year  of  his  age  to 
his  young  friend,  Francis  Aston,  Esq.,  who  was  about 
to  set  out  on  his  travels.  This  letter  is  a  highly 
interesting  production ;  and  while  it  shows  much 
knowledge  of  the  human  heart,  it  throws  a  strong 
light  upon  the  character  and  opinions  of  its  author. 

In  his  personal  appearance,  Sir  Isaac  Newton  was 
not  above  the  middle  size,  and  in  the  latter  part  of 
his  life  was  inclined  to  be  corpulent.  According  to 
Mr.  Conduit  "  he  had  a  very  lively  and  piercing  eye, 
a  comely  and  gracious  aspect,  with  a  fine  head  of 
hair  as  white  as  silver,  without  any  baldness,  and 
when  his  peruke  was  off  was  a  venerable  sight." 
Bishop  Atterbury  asserts,!  on  the  other  hand,  that 
the  lively  and  piercing  eye  did  not  belong  to  Sir 
Isaac  during  the  last  twenty  years  of  his  life.  "  In- 
deed," says  he,  "  in  the  whole  air  of  his  face  and 
make  there  was  nothing  of  that  penetrating  sagacity 
which  appears  in  his  compositions.  He  had  some- 
thing rather  languid  in  his  look  and  manner  which 
did  not  raise  any  great  expectation  in  those  who  did 
not  know  him."  This  opinion  of  Bishop  Atterbury 
is  confirmed  by  an  observation  of  Mr.  Thomas 

*  The  following  anecdote  of  Sir  Isaac's  absence  has  been  published, 
but  I  cannot  vouch  for  its  authenticity.  His  intimate  friend  Dr.  Stukely, 
•who  had  been  deputy  to  Dr.  Hailey  as  secretary  to  the  Royal  Society, 
was  one  day  shown  into  Sir  Isaac's  dining-room,  where  his  dinner  had 
been  for  some  time  served  up.  Dr.  Stukely  waited  for  a  considerable 
*ime,  and  getting  impatient,  he  removed  the  cover  from  a  chicken,  which 
he  ate,  replacing  the  bones  under  the  cover.  In  a  short  time  Sir  Isaac 
entered  the  room,  and  after  the  usual  compliments  sat  down  to  his  din- 
ner, but  on  taking  off  tne  cover,  and  seeing  nothing  but  bones,  he  re- 
marked, "  How  absent  we  philosophers  are.  I  really  thought  that  1 I)p4 
BOt  dined." 

t  Epistolary  Correspondence,  vol.  i.  p.  180,  sec.  71 


304  SIR  ISAAC  NEWTON. 

<r 

Hearne,*  who  says  "  that  Sir  Isaac  was  a  man  of  no 
very  promising  aspect.  He  was  a  short,  well-set 
man.  He  was  full  of  thought,  and  spoke  very  little  in 
company,  so  that  his  conversation  was  not  agreeable. 
When  he  rode  in  his  coach,  one  arm  would  be  out 
of  his  coach  on  one  side  and  the  other  on  the  other." 
Sir  Isaac  never  wore  spectacles,  and  never  "  lost 
more  than  one  tooth  to  the  day  of  his  death." 

Besides  the  statue  of  S\r  Isaac  Newton  executed 
by  Roubiliac,  there  is  a  bust  of  him  by  the  same 
artist  in  the  library  of  Trinity  College,  Cambridge. 
Several  good  paintings  of  him  are  extant.  Two 
of  these  are  in  the  hall  of  the  Royal  Society  of 
London,  and  have,  we  believe,  been  often  engraved. 
Another,  by  Vanderbank,  is  in  the  apartments  of 
the  Master's  lodge  in  Trinity  College,  and  has  been 
engraved  by  Vertue.  Another,  by  Valentine  Ritts, 
is  in  the  landing-place  near  the  entrance  to  Trinity 
College  library ;  but  the  best,  from  which  our  en- 
graving is  copied,  was  painted  by  Sir  Godfrey  Knel- 
ler,  and  is  in  the  possession  of  Lord  Egremont  at 
Petworth.  In  the  university  library  there  is  pre- 
served a  cast  taken  from  his  face  after  death. 

Every  memorial  of  so  great  a  man  as  Sir  Isaac 
Newton  has  been  preserved  and  cherished  with  pecu- 
liar veneration.  His  house  at  Woolsthorpe,  of  which 
we  have  given  an  engraving,  has  been. religiously 
protected  by  Mr.  Tumor  of  Stoke  Rocheford,  the 
proprietor.  Dr.  Stukeley,  who  visited  it  in  Sir 
Isaac's  lifetime,  on  the  13th  October,  1721,  gives  the 
following  description  of  it  in  his  letter  to  Dr.  Mead, 
written  in  1727 :  "  'Tis  built  of  stone  as  is  the  way 
of  the  country  hereabouts,  and  a  reasonable  good 
one.  They  led  me  up  stairs  and  showed  me  Sir 
Isaac's  study,  where  I  suppose  he  studied  when  in 
the  country  in  his  younger  days,  or  perhaps  when 
he  visited  his  mother  from  the  university.  I  ob- 
served the  shelves  were  of  his  own  making,  being 
pieces  of  deal  boxes  which  probably  he  sent  his 
*  MS.  Memoranda  in  the  Bodleian  Library. 


MEMORIALS   AND  RECOLLECTIONS.  305 

books  and  clothes  down  in  on  those  occasions. 

There  were  some  years  ago  two  or  three  hundred 
j  books  in  it  of  his  father-in-law,  Mr.  Smith,  which 

Sir  Isaac  gave  to  Dr.  Newton  of  our  town."* 

When  the  house  was  repaired  in  1798,  a  tablet  of 
i  white  marble  was  put  up  by  Mr.  Turnor  in  the  room 
[where  Sir  Isaac  was  born,  with  the  following  in- 
I  scription : 

"  Sir  Isaac  Newton,  son  of  John  Newton,  Lord 
I  of  the  manor  of  Woolsthorpe,  was  born  in  this  room 

on  the  25th  December,  1642." 

Nature  and  Nature's  laws  lay  hid  in  nign*, 
God  said,  '*  Let  Newton  be,"  and  all  was  light. 

The  following  lines  have  been  written  upon  the 
house : 

Here  Newton  dawned,  here  lofty  wisdom  woke, 

And  to  a  wondering  world  divinely  spoke. 

If  Tully  glowed,  when  Phaedrus'  steps  he  trode, 

Or  fancy  formed  Philosophy  a  god ; 

If  sages  still  for  Homer's  birth  contend 

The  Sons  of  Science  at  this  dome  must  bend. 

All  hail  the  shrine  !  All  hail  the  natal  day, 

Cam  boasts  his  noon,— This  Cot  his  morning  ray. 

The  house  is  now  occupied  by  a  person  of  the 
name  of  John  Wollerton.  It  still  contains  the  two 
dials  made  by  Newton,  but  the  styles  of  both  are 
wanting.  The  celebrated  apple-tree,  the  fall  of  one 
of  the  apples  of  which  is  said  to  have  turned  the 
attention  of  Newton  to  the  subject  of  gravity,  was 
destroyed  by  wind  about  four  years  ago ;  but  Mr. 
Turnor  has  preserved  it  in  the  form  of  a  chair,  f 

The  chambers  which  Sir  Isaac  inhabited  at  Cam- 
bridge are  known  by  tradition.  They  are  the  apart- 
ments next  to  the  great  gate  of  Trinity  College,  and 
it  is  believed  that  they  then  communicated  by  a 
staircase  with  the  observatory  in  the  Great  Tower, 

*  Tumor's  Collections,  p.  176. 

t  The  anecdote  of  the  falling  apple  is  mentioned  neither  by  Dr.  StuVely 
or  by  Mr.  Conduit,  and  as  I  have  not  been  able  to  find  any  authority  for 
it  whatever,  I  did  not  feel  myself  at  liberty  to  use  it. 

Cc2 


306  SIR    ISAAC    NEWTON, 

— an  observatory  which  was  furnished  by  the  contri 
butions  of  Newton,  Cotes,  and  others.  His  telescope, 
represented  in  fig.  1,  page  41,  is  preserved  in  the 
library  of  the  Royal  Society  of  London,  and  his  globe, 
his  universal  ring-dial,  quadrant,  compass,  and  a  re- 
flecting telescope  said  to  have  belonged  to  him,  in 
the  library  of  Trinity  College.  There  is  also  in  the 
same  collection  a  long  and  curled  lock  of  his  sih  er 
white  hair.  The  door  of  his  bookcase  is  in  the  Mu- 
seum of  the  Royal  Society  of  Edinburgh. 

The  manuscripts,  letters,  and  other  papers  of  New- 
ton have  been  preserved  in  different  collections.  His 
correspondence  with  Cotes  relative  to  the  second 
edition  of  the  Principia,  and  amounting  to  between 
sixty  and  a  hundred  letters,  a  considerable  portion 
of  the  manuscript  of  that  work,  and  two  or  three 
letters  to  Dr.  Keill  on  the  Leibnitzian  controversy, 
are  preserved  in  the  library  of  Trinity  College,  Cam- 
bridge. Newton's  letters  to  Flamstead,  about  thirty- 
four  in  number,  are  deposited  in  the  library  of  Corpus 
Christi  College,  Oxford.*  Several  letters  of  New- 
ton, and,  we  believe,  the  original  specimen  which  he 
drew  up  of  the  Principia,  exist  among  the  papers  of 
Mr.  William  Jones  (the  father  of  Sir  William  Jones), 
which  are  preserved  at  Shirburn  Castle,  in  the  library 
of  Lord  Macclesfield.  But  the  great  mass  of  New- 
ton's papers  came  into  the  possession  of  the  Ports- 
mouth family  through  his  niece,  Lady  Lymington, 
and  have  been  safely  preserved  by  that  noble  family. 
There  is  reason  to  believe  that  they  contain  nothing 
which  could  be  peculiarly  interesting  to  science ;  but 
as  the  correspondence  of  Newton  with  contempo- 
rary philosophers  must  throw  considerable  light  on 
his  personal  history,  we  trust  that  it  will  ere  long  be 
given  to  the  public. 

*  In  the  Monthly  Review  for  August,  1829,  p.  593,  it  is  stated,  that  the 
correspondence  between  Newton  and  Flamstead,  from  1680  to  1698,  exists 
in  the  Sloane  collection  of  Manuscripts  in  the  British  Museum.  Pro- 
fessor Rigaud,  however,  has  had  the  kindness  to  inquire  into  the  accuracy 
of  this  statement,  ana  he  has  ascertained  that  these  letters  are  merely 
copies,  which., Dr.  Birch  had  made  from  the  originals  at  Oxford. 


(907) 


APPENDIX. 

No.  I. 

OBSERVATIONS   ON  THE   FAMILY   OF   SIR  ISAAC   NEWTON.  * 

IN  the  year  1705,  Sir  Isaac  gave  into  the  Herald's 
Office  an  elaborate  pedigree,  stating  upon  oath  that 
Tie  had  reason  to  believe  that  John  Newton  of  Westby, 
n  the  county  of  Lincoln,  was  his  great-grandfather's 
ather,  and  that  this  was  the  same  John  Newton  who 
was  buried  in  Basingthorpe  church,  on  the  22d  De- 
cember, 1563.  This  John  Newton  had  four  sons, 
'ohn,  Thomas,  Richard,  and  William  Newton  of 
runnerly,  the  last  of  whom  was  great-grandfather 
o  Sir  John  Newton,  Bart.,  of  Hather.  Sir  Isaac 
considered  himself  as  descended  from  the  eldest  of 
;hese,  he  having^  by  tradition  from  his  kindred  ever 
since  he  can  remember,  reckoned  himself  next  of  kin 
among  the  Newtons)  to  Sir  John  Newton's  family. 

The  pedigree,  founded  upon  these  and  other  con- 
iderations,  was  accompanied  by  a  certificate  from 
Sir  John  Newton,  of  Thorpe,  Bart.,  who  states  that 
hie  had  heard  his  father  speak  of  Sir  Isaac  Newton 
s  of  his  relation  and  kinsman,  and  that  he  himself 
elieved  that  Sir  Isaac  was  descended  from  John  New- 
on,  son  to  John  Newton  of  Westby,  but  knoweth  not  in 
mat  particular  manner. 

The  pedigree  of  Sir  Isaac,  as  entered  at  the  Her- 
Id's  Office,  does  not  seem  to  have  been  satisfactory 
ither  to  himself  or  to  his  successors,  as  it  could  not 


308  APPENDIX. 

be  traced  with  certainty  beyond  his  grandfather ;  and 
it  will  be  seen  from  the  following'interesting  corres- 
pondence, that  upon  making  further  researches,  he 
had  found  some  reason  to  believe  that  he  was  of 
Scotch  extraction. 

"Extract  of  a  Letter  from  the  Reverend  Dr.  Reid  of 
Glasgow  to  Dr.  Gregory  of  Edinburgh,  dated  14^7 
March,  1784. 

"  I  send  you  on  the  other  page  an  anecdote  re 
specting  Sir  Isaac  Newton,  which  I  do  not  remem- 
ber whether  I  ever  happened  to  mention  to  you  in 
conversation.  If  his  descent  be  not  clearly  ascer- 
tained (as  I  think  it  is  not  in  the  books  I  have  seen), 
might  it  not  be  worth  while  to  inquire  if  evidence 
can  be  found  to  confirm  the  account  which  he  is  said 
to  have  given  of  himself.  Sheriff  Cross  was  very 
zealous  about  it  when  death  put  a  stop  to  his  in- 
quiries. 

!  "When  I  lived  in  old  Aberdeen  above  twenty 
years  ago,  I  happened  to  be  conversing  over  a  pipe 
of  tobacco  with  a  gentleman  of  that  country,  who 
had  been  lately  at  Edinburgh.  He  told  me  that  he 
had  been  often  in  company  with  Mr.  Hepburn  of 
Keith,  with  whom  I  had  the  honour  of  some  ac- 
quaintance. He  said  that,  speaking  of  Sir  Isaac 
Newton,  Mr.  Hepburn  mentioned  an  anecdote,  which 
he  had  from  Mr.  James  Gregory,  professor  of  mathe- 
matics at  Edinburgh,  which  was  to  this  purpose  : 

"  Mr.  Gregory,  being  at  London  for  some  time 
after  he  resigned  the  mathematical  chair,  was  often 
with  Sir  Isaac  Newton.  One  day  Sir  Isaac  said  to 
him,  '  Gregory,  I  believe  you  don't  know  that  I  am 
connected  with  Scotland-' — '  Pray  how,  Sir  Isaac  V 
said  Gregory.  Sir  Isaac  said  he  was  told  that  his 
grandfather  was  a  gentleman  of  East  Lothian ;  that 
he  came  to  London  with  King  James  si  his  acces- 
sion to  the  crown  of  England,  and  there  spent  his 


APPENDIX.  309 

brtune,  as  many  more  did  at  that  time,  by  which  his 
jon  (Sir  Isaac's  father)  was  reduced  to  mean  cir- 
cumstances. To  this  Gregory  bluntly  replied, 
Newton  a  gentleman  of  East  Lothian,  I  never 
leard  of  a  gentleman  of  East  Lothian  of  that  name.' 
Jpon  this  Sir  Isaac  said,  '  that  being  very  young 

en  his  father  died,  he  had  it  only  by  tradition, 
ind  it  might  be  a  mistake ;'  and  immediately  turned 
;he  conversation  to  another  subject. 

"  I  confess  I  suspected  that  the  gentleman  who 
was  my  author  had  given  some  colouring  to  this 
story,  and  therefore  I  never  mentioned  it  for  a  good 
nany  years. 

"  After  I  removed  to  Glasgow,  I  came  to  be  very 
intimately  acquainted  with  Mr.  Cross,  then  sheriff 
)f  Lanark,  and  one  day  at  his  own  house  mentioned 
;his  story,  without  naming  my  author,  of  whom  I 
expressed  some  diffidence. 

"  The  sheriff  immediately  took  it  up  as  a  matter 
worth  being  inquired  into.  He  said  he  was  well 
acquainted  with  Mr.  Hepburn  of  Keith  (who  was 
;hen  alive),  and  that  he  would  write  him  to  know 
whether  he  ever  heard  Mr.  Gregory  say  that  he  had 
such  a  conversation  with  Sir  Isaac  Newton.  He 
said  he  knew  that  Mr.  Keith,  the  ambassador,  was 
also  intimate  with  Mr.  Gregory,  and  that  he  would 
write  him  to  the  same  purpose. 

"  Some  time  after,  Mr.  Cross  told  me  that  he  had 
answers  from  both  the  gentlemen  above  mentioned, 
and  that  both  remembered  to  have  heard  Mr.  Greg- 
ory mention  the  conversation  between  him  and  Sir 
Isaac  Newton,  to  the  purpose  above  narrated,  and 
at  the  same  time  acknowledged  that  they  had  made 
no  further  inquiry  about  the  matter. 

"  Mr.  Cross,  however,  continued  the  inquiry,  and 
a  short  time  before  his  death  told  me  that  all  he 
had  learned  was,  that  there  is,  or  was  lately,  a  baro- 
net's family  of  the  name  of  Newton  in  West  Lothian 
Mid  Lothian  (I  have  forgot  which) :  that  there  is 


310  APPENDIX. 

a  tradition  in  that  family  that  Sir  Isaac  Newto 
wrote  a  letter  to  the  old  knight  that  then  was  ( 
think  Sir  John  Newton  of  Newton  was  his  name] 
desiring  to  know  what  children,  and  particular!; 
what  sons  he  had,  their  age,  and  what  profession 
they  intended :  that  the  old  baronet  never  deigne 
to  return  an  answer  to  this  letter,  which  his  famil 
was  sorry  for,  as  they  thought  Sir  Isaac  might  hav 
intended  to  do  something  for  them." 

Several  years  after  this  letter  was  written,  a  Mi* 
Barren,  a  relation  of  Sir  Isaac  Newton,  seems  t 
have  been  making  inquiries  respecting  the  famil; 
of  his  ancestor,  and  in  consequence  of  this  the  lat 
Professor  Robison  applied  to  Dr.  Reid,  to  obtai 
from  him  a  more  particular  account  of  the  remark 
able  conversation  between  Sir  Isaac  and  Mr.  Jame 
Gregory  referred  to  in  the  preceding  letter.  I: 
answer  to  this  request,  Dr.  Reid  wrote  the  followin 
letter,  for  which  I  was  indebted  to  John  Robisor 
Esq.  Sec.  R.  S.  E.,  who  found  it  among  Ms  father' 
manuscripts. 

Letter  from  Dr.  Reid  to  Professor  Robison  respecting 
the  Family  of  Sir  Isaac  Newton. 

"  DEAR  SIR, 

"  I  am  very  glad  to  learn  by  yours  of  April  4,  tha 
a  Mr.  Barron,  a  near  relation  of  Sir  Isaac  Newton 
is  anxious  to  inquire  into  the  descent  of  that  grea 
man,  as  the  family  cannot  trace  it  farther,  with  an; 
certainty,  than  his  grandfather.  I  therefore,  as  yoi 
desire,  send  you  a  precise  account  of  all  I  know 
and  am  glad  to  have  this  opportunity,  before  I  die 
of  putting  this  information  in  hands  that  will  mak 
the  proper  use  of  it,  if  it  shall  be  found  of  any  use 

"  Several  years  before  I  left  Aberdeen  (which 
did  in  1764),  Mr.  Douglas  of  Feckel,  the  father  o 
Sylvester  Douglas,  now  a  barrister  at  London,  tol 


APPENDIX.  311 

ne,  that  having  been  lately  at  Edinburgh,  he  was 
)ften  in  company  with  Mr.  Hepburn  of  Keith,  a 
gentleman  of  whom  I  had  some  acquaintance,  by 
lis  lodging  a  night  at  my  house  at  New  Machar, 
vhen  he  was  in  the  rebel  army  in  1745.  That  Mr. 
lepburn  told  him  that  he  had  heard  Mr.  James 
jiregory,  professor  of  mathematics,  Edinburgh,  say, 
hat  being  one  day  in  familiar  conversation  with 
Sir  Isaac  Newton  at  London,  Sir  Isaac  said,  '  Greg- 
ory, I  believe  you  don't  know  that  I  am  a  Scotch- 
nan.' — '  Pray,"  how  is  that  ]'  said  Gregory.  Sir 
saac  said  he  was  informed  that  his  grandfather  (or 
freat-grand  father)  was  a  gentleman  of  East  (or 
Yest)  Lothian :  that  he  went  to  London  with  King 
ames  the  I.  at  his  accession  to  the  crown  of  Eng- 
and :  and  that  he  attended  the  court  in  expectation, 
s  many  others  did,  until  he  spent  his  fortune,  by 
vhich  means  his  family  was  reduced  to  low  circum- 
tances.  At  the  time  this  was  told  me  Mr.  Gregory 
vas  dead,  otherwise  I  should  have  had  his  own  tes- 
imony,  for  he  was  my  mother's  brother.  I  likewise 
bought  at  that  time  that  it  had  been  certainly  known 
tiat  Sir  Isaac  had  been  descended  from  an  old  English 
amily,  as  I  think  is  said  in  his  eloge  before  the 
Academy  of  Sciences  at  Paris,  and  therefore  I  never 
nentioned  what  I  had  heard  for  many  years,  be- 
teving  that  there  must  be  some  mistake  in  it. 

"  Some  years  after  I  came  to  Glasgow,  I  men- 
ioned  (I  believe  for  the  first  time)  what  I  had  heard 
o  have  been  said  by  Mr.  Hepburn  to  Mr.  Cross,  late 
heriff  of  this  county,  whom  you  will  remember. 
Ir.  Cross  was  moved  by  this  account,  and  imme- 
iately  said, 1 1  know  Mr.  Hepburn  very  well,  and  I 
.now  he  was  intimate  with  Mr.  Gregory :  I  shall 
vrite  him  this  same  night,  to  know  whether  he 
leard  Mr.  Gregory  say  so  or  not.'  After  some  re- 
lection,  he  added,  *  I  know  that  Mr.  Keith,  the  am- 
assador,  was  also  an  intimate  acquaintance  of  Mr. 
Gregory,  and  as  he  is  at  present  in  Edinburgh,  I 
hall  likewise  write  to  him  this  night.* 


812  APPENDIX. 

"  The  next  time  I  waited  on  Mr.  Cross  he  told 
me  that  he  had  wrote  both  to  Mr.  Hepburn  and  Mr*« 
Keith,  and  had  an  answer  from  both,  and  that  both  of 
them  testified  that  they  had  several  times  heard  Mr<s 
James  Gregory  say,  that  Sir  Isaac  Newton  told  him; 
what  is  above  expressed,  but  that  neither  they  noc 
Mr.  Gregory,  as  far  as  they  knew,  ever  made  any* 
further  inquiry  into  the  matter.  This  appeared  very 
strange  both  to  Mr.  Cross  and  me,  and  he  said -hat 
would  reproach  them  for  their  indifference,  and 
would  make  inquiry  as  soon  as  he  was  able. 

"  He  lived  but  a  short  time  after  this,  and  in  the 
last  conversation  I  had  with  him  upon  the  subject^ 
he  said,  that  all  he  had  yet  learned  was,  that  there 
was  a  Sir  John  Newton  of  Newton  in  one  of  the 
counties  of  Lothian  (but  I  have  forgot  which),  somd 
of  whose  chLdren  were  yet  alive  :  that  they  reported 
that  their  father,  Sir  John,  had  a  letter  from  Sir 
Isaac  Newton,  desiring  to  know  the  state  of  hia 
family,  what  children  he  had,  particularly  what  sons^ 
and  in  what  way  they  were.  The  old  knight  neve? 
returned  an  answer  to  this  letter,  thinking  probably 
that  Sir  Isaac  was  some  upstart,  who  wanted  to 
claim  a  relation  to  his  worshipful  house.  This  omis* 
sion  the  children  regretted,  conceiving  that  Sir  Isaac 
might  have  had  a  view  of  doing  something  for  their 
benefit. 

"  After  this  I  mentioned  occasionally  in  conver- 
sation what  I  knew,  hoping  that  these  facts  might 
lead  to  some  more  certain  discovery,  but  I  found 
more  coldness  about  the  matter  than  I  thought  it 
deserved.  I  wrote  an  account  of  it  to  Dr.  Gregory, 
your  colleague,  that  he  might  impart  it  to  any  mem- 
ber of  the  Antiquarian  Society  who  he  judged 
might  have  the  curiosity  to  trace  the  matter  further. 

"In  the  year   1787,  my  colleague,  Mr.  Patrick 
Wilson,  professor  of   astronomy,  having  been  in  j 
London,  told  me  on  his  return  that  he  had  met  ac- 
cidentally with  a  James  Hutton,  Esq.  of  Pimlico, 


APPENDIX.  313 

Westminster,  a  near  relation  of  Sir  Isaac  Newton,* 
to  whom  he  mentioned  what  he  had  heard  from  me 
with  respect  to  Sir  Isaac's  descent,  and  that  I  wished 
much  to  know  something  more  decisive  on  that  sub- 
ject. Mr.  Hutton  said,  if  I  pleased  to  write  to  him 
he  would  give  me  all  the  information  he  could  give. 
I  wrote  him  accordingly,  and  had  a  very  polite 
answer,  dated  at  Bath,  25th  December,  1787,  which  is 
now  before  me.  He  says, '  I  shall  be  glad  when  I 
return  to  London,  if  I  can  find  in  some  old  notes  of 
my  mother  any  thing  that  may  fix  the  certainty  of 
Sir  Isaac's  descent.  If  he  spoke  so  to  Mr.  James 
Gregory,  it  is  most  certain  he  spoke  truth.  But  Sir 
Isaac's  grandfather,  not  his  great-grandfather,  must 
be  the  person  who  came  from  Scotland  with  King 
James  I.  If  I  find  any  thing  to  the  purpose,  I  will 
take  care  it  shall  reach  you.' 

"  In  consequence  of  this  letter  I  expected  another 
from  Mr.  Hutton  when  he  should  return  to  London, 
but  have  never  had  any.  Mr.  Wilson  told  me  he 
was  a  very  old  man,  and  whether  he  be  dead  or  alive 
I  know  not. 

"  This  is  all  I  know  of  the  matter,  and  for  the 
facts  above  mentioned  I  pledge  my  veracity.  I 
am  much  obliged  to  you,  dear  sir,  for  the  kind  ex- 
pressions of  your  affection  and  esteem,  which,  I 
assure  you,  are  mutual  on  my  part,  and  I  sincerely 
sympathize  with  you  on  your  afflicting  state  of 
health,  which  makes  you  consider  yourself  as  out 
of  the  world,  and  despair  of  seeing  me  any  more. 

"  I  have  been  long  out  of  the  world  by  deafness 
and  extreme  old  age.  I  hope,  however,  if  we  should 
not  meet  again  in  this  world,  that  we  shall  meet  and 
renew  our  acquaintance  in  another.  In  the  mean 
time,  I  am  with  great  esteem,  dear  sir,  yours  affec- 
tionately, "  THO.  REID. 

"  Glasgow  College, 
" 
See  page  288,  note. 

Dd 


314  APPENDIX. 

This  curious  letter  I  published  in  the  Ed.  Phil. 
Journal  for  October  1, 1820.  It  excited  the  particular 
attention  of  the  late  George  Chalmers,  Esq.,  who 
sent  me  an  elaborate  letter  upon  the  subject ;  but  as 
I  was  at  that  time  in  the  expectation  of  obtaining 
some  important  information  through  other  channels, 
this  letter  was  not  published.  This  hope,  however, 
has  been  disappointed.  A  careful  search  has  been 
made  through  the  charter-chest  of  the  Newtons 
of  Newton  in  East  Lothian,  by  Mr.  Richard  Play 
Newton,  the  representative  of  that  family,  but  no 
document  whatever  has  been  found  that  can  throw 
the  least  light  upon  the  matter.  It  deserves  to  be 
remarked,  however,  that  Sir  Richard  Newton,  the 
alleged  correspondent  of  Sir  Isaac,  appears  to  have 
destroyed  his  correspondence ;  for  though  the  char- 
ter-chest contains  the  letters  of  his  predecessors  for 
some  generations,  yet  there  is  not  a  single  epistolary 
document  either  of  his  own  or  of  his  lady's. 

Hitherto  the  evidence  of  Sir  Isaac's  Scottish  de- 
scent has  been  derived  chiefly  from  his  conversation 
with  Mr.  James  Gregory ;  but  I  am  enabled,  by  the 
kindness  of  Mr.  Robison,  to  corroborate  this  evi- 
dence by  the  following  information,  derived,  as  will 
be  .seen,  from  the  family  of  the  Newtons  of  Newton. 
Among  various  memoranda  in  the  handwriting  of 
Professor  Robison,  who  at  one  time  proposed  to 
write  the  life  of  Sir  Isaac,  are  the  following : — 

"  1st,  Lord  Henderland  informed  me  in  a  letter 
dated  March,  1794,  that  he  had  heard  from  his  infancy 
that  Sir  Isaac  considered  himself  as  descended  from 
the  family  of  Newton  of  Newton.  This  he  heard 
from  his  uncle  Richard  Newton  of  Newton  (who 
was  third  son  of  Lord  William  Hay  of  Newhall) :" 
"  He  said  that  Sir  Isaac  wrote  to  Scotland  to  learn 
whether  any  descendants  of  that  family  remained, 
and  this  (it  was  thought)  with  the  view  to  leave 
some  of  his  fortune  to  the  family  possessing  the 
estate  with  the  title  of  baronet.  Mr.  Newton,  not 


APPENDIX*  315 

laving  this  honour,  and  being  a  shy  man,  did  not 
encourage  the  correspondence,  because  he  did  not 
considei  himself  as  of  kin  to  Sir  Isaac,  &c." 

"  2d,  Information  communicated  to  me  by  Hay 
Newton,  Esq.,  of  that  ilk,  18th  August,  1800." 

The  late  Sir  Richard  Newton  of  Newton,  Bart, 
chief  of  that  name,  having  no  male  children,  settled 
;he  estate  and  barony  of  Newton  in  East  Lothian 
county  upon  his  relation  Richard  Hay  Newton,  Esq., 
son  of  Lord  William  Hay."* — "  It  cannot  be  dis- 
covered how  long  the  family  of  Newton  have  been 
n  possession  of  the  barony,  there  being  no  tradition 
concerning  that  circumstance  further  than  that  they 
came  originally  from  England  at  a  very  distant 
)eriod,  and  settled  on  these  lands." — "  The  celebrated 
Sir  Isaac  Newton  was  a  distant  relation  of  the 
family,  and  corresponded  with  the  last  baronet,  the 
above-mentioned  Sir  Richard  Newton." 

The  preceding  documents  furnish  the  most  com- 
pete evidence  that  the  conversation  respecting  Sir 
'saac  Newton's  family  took  place  between  him  and 
Mr.  Gregory;  and  the  testimony  of  Lord  Henderland 
>roves  that  his  own  uncle,  Richard  Newton  of  New- 
on,  the  immediate  successor  of  Sir  Richard  Newton, 
with  whom  Sir  Isaac  corresponded,  was  perfectly 
confident  that  such  a  correspondence  took  place. 

All  these  circumstances  prove  that  Sir  Isaac  New- 
ton could  not  trace  his  pedigree  with  any  certainty 
beyond  his  grandfather,  and  that  there  were  two  dif- 
ferent traditions  in  his  family, — one  which  referred 
his  descent  to  John  Newton  of  Westby,  and  the 
other  to  a  gentleman  of  East  Lothian  who  accom- 
panied King  James  VI.  to  England.  In  the  first  of 
these  traditions  he  seems  to  have  placed  most  confi- 
dence in  1705,  when  he  drew  out  his  traditionary 
pedigree ;  but  as  the  conversation  w  ith  Professor 
James  Gregory  respecting  his  Scotch  extraction 

*  This  entail  was  executed  in  1724.  a  year  or  two  before  Sir  Richard's 
.— D.  B. 


316  APPENDIX. 

tooK  place  twenty  years  afterward,  namely,  between 
1725  and  1727,  it  is  probable  that  he  had  discovered 
the  incorrectness  of  his  first  opinions,  or  at  least 
was  disposed  to  attach  more  importance  to  the  other 
tradition  respecting  his  descent  from  a  Scotch  family. 
In  the  letter  addressed  to  me  by  the  learned  George 
Chalmers,  Esq.  I  find  the  following  observations 
respecting  the  immediate  relations  of  Sir  Isaac. 
"  The  Newtons  of  Woolsthorpe,"  says  he,  "  who 
were  merely  yeomen  farmers,  were  not  by  any 
means  opulent.  The  son  of  Sir  Isaac's  father's 
brother  was  a  carpenter  called  John.  He  was  after- 
ward appointed  gamekeeper  to  Sir  Isaac,  as  lord 
of  the  manor,  and  died  at  the  age  of  sixty  in  1725. 
This  John  had  a  son,  Robert,  (John?)  who  was 
Sir  Isaac's  second  cousin,  and  who  became  possessed 
of  the  whole  land  estates  at  and  near  Woolsthorpe, 
which  belonged  to  the  great  Newton,  as  his  heir-at- 
law.*  Robert  (John  1)  became  a  worthless  and  disso- 
lute pers'on,  who  very  soon  wasted  this  ancient  patri- 
mony, and  falling  down  with  a  tobacco-pipe  in  his 
mouth  when  he  was  drunk,  it  broke  in  his  throat, 
and  put  an  end  to  his  life  at  the  age  of  thirty  years, 
in  1737." 

No.  II. 

LETTER  FROM  SIR  ISAAC  NEWTON  TO  FRANCIS  ASTON, 
ESQ.,  A  YOUNG  FRIEND  WHO  WAS  ON  THE  EVE  OF  SET- 
TING OUT  UPON  HIS  TRAVELS. 

MR.  ASTON  was  elected  a  Fellow  of  the  Royal 
Society  in  1678.  He  held  the  office  of  Secretary 
between  1681  and  1685 ;  and  he  was  the  author  of 
some  observations  on  certain  unknown  ancient  char- 
acters, which  were  published  in  the  Philosophical 
Transactions  for  1693. 

*  See  p.  291. 


APPENDIX.  317 

This  letter  has  been  referred  to  in  pages  270  and 
303,  and  was  written  when  Newton  was  only  twen- 
ty-six years  of  age.  It  is  in  every  respect  an  inter- 
esting document. 

"  Trinity  College^Canibridge^ 
"  SIR,  May  18,  1669. 

"  Since  in  your  letter  you  give  mee  so  much 
liberty  of  spending  my  judgement  about  what  may 
be  to  your  advantage  in  travelling,  I  shall  do  it 
more  freely  than  perhaps  otherwise  would  have 
been  decent.  First,  then,  I  will  lay  down  some 
general  rules,  most  of  which,  I  believe,  you  have 
considered  already ;  but  if  any  of  them  be  new  to 
you,  they  may  excuse  the  rest ;  if  none  at  all,  yet 
is  my  punishment  more  in  writing  than  yours  in 
reading. 

"  When  you  come  into  any  fresh  company,  1. 
Observe  their  humours.  2.  Suit  your  own  carriage 
thereto,  by  which  insinuation  you  will  make  their 
converse  more  free  and  open.'  3.  Let  your  dis- 
corrs  be  more  in  querys  and  doubtings  than  peremp- 
tory assertions  or  disputings,  it  being  the  designe 
of  travellers  to  learne,  not  to  teach.  Besides,  it  will 
persuade  your  acquaintance  that  you  have  the  greater 
esteem  of  them,  and  soe  make  them  more  ready 
to  communicate  what  they  know  to  you ;  whereas 
nothing  sooner  occasions  disrespect  and  quarrels 
than  peremtorinesse.  You  will  find  little  or  no 
advantage  in  seeming  wiser  or  much  more  ignorant 
than  your  company.  4.  Seldom  discommend  any 
thing  though  never  so  bad,  or  doe  it  but  moderately, 
lest  you  bee  unexpectedly  forced  to  an  unhansom 
retraction.  It  is  safer  to  commend  any  thing  more 
than  it  deserves,  than  to  discommend  a  thing  soe 
much  as  it  deserves ;  for  commendations  meet  no" 
soe  often  with  oppositions,  or,  at  least,  are  no*" 
usually  soe  ill  resented  by  men  that  think  otherwise, 
as  discommendations ;  and  you  will  insinuate  into 


318  APPENDIX. 

men's  favour  by  nothing  sooner  than  seeming'  to 
approve  and  commend  what  they  like ;  but  beware 
of  doing  it  by  a  comparison.  5.  If  you  bee  affronted, 
it  is  better,  in  a  forraine  country,  to  pass  it  by  in 
silence,  and  with  a  jest,  though  with  some  dishonour, 
than  to  endeavour  revenge ;  for,  in  the  first  case, 
your  credit's  ne'er  the  worse  when  you  return  into 
England,  or  come  into  other  company  that  have  not 
heard  of  the  quarrell.  But,  in  the  second  case,  you 
may  beare  the  marks  of  the  quarrell  while  you  live, 
if  you  outlive  it  at  all.  But,  if  you  find  yourself  un- 
avoidably engaged,  'tis  best,  I  think,  if  you  can  com- 
mand your  passion  and  language,  to  keep  them 
pretty  evenly  at  some  certain  moderate  pitch,  not 
much  hightning  them  to  exasperate  your  adversary, 
or  provoke  his  friends,  nor  letting  them  grow  over- 
much dejected  to  make  him  insult.  In  a  word,  if 
you  can  keep  reason  above  passion,  that  and  watch- 
fullnesse  will  be  your  best  defendants.  To  which 
purpose  you  may  consider,  that,  though  such  excuses 
as  this, — He  provok't  mee  so  much  I  could  not  for- 
bear,— may  pass  among  friends,  yet  amongst  stran- 
gers they  are  insignificant,  and  only  argue  a  travel- 
ler's weaknesse. 

"  To  these  I  may  add  some  general  heads  for  in- 
quirys  or  observations,  such  as  at  present  I  can 
think  on.  As,  1.  To  observe  the  policy s,  wealth, 
and  state-affairs  of  nations,  so  far  as  a  solitary 
traveller  may  conveniently  doe.  2.  Their  imposi- 
tions upon  all  sorts  of  people,  trades,  or  commoditys, 
that  are  remarkable.  3.  Their  laws  and  customs, 
how  far  they  differ  from  ours.  4.  Their  trades  and 
arts  wherein  they  excell  or  come  short  of  us  in 
England.  5.  Such  fortifications  as  you  shall  meet 
with,  their  fashion,  strength,  and  advantages  for  de- 
fence, and  other  such  military  affairs  as  are  consider- 
able. 6.  The  power  and  respect  belonging  to  their 
degrees  of  nobility  or  magistracy.  7.  It  will  not  be 
time  mispent  to  make  a  catalogue  of  the  names  and 


APPENDIX.  319 

excellencys  of  those  men  that  are  most  wise,  learned, 
or  esteemed  in  any  nation.  8.  Observe  the  mecha- 
nisme  and  manner  of  guiding  ships.  9.  Observe  the 
products  oi  nature  in  several  places,  especially  in 
mines,  with  the  circumstances  of  mining  arid  of  ex- 
tracting metals  or  minerals  out  of  their  oare,  and  of 
refining  them ;  and  if  you  meet  with  any  transmuta- 
tions out  of  their  own  species  into  another  (as  out 
of  iron  into  copper,  out  of  any  metall  into  quicksilver, 
out  of  one  salt  into  another,  or  into  an  insipid  body, 
&c.),  those,  above  all,  will  be  worth  your  noting, 
being  the  most  luciferous,  and  many  times  lucrife- 
rous  experiments  too,  in  philosophy.  10.  The  prices 
of  diet  and  other  things.  11.  And  the  staple  com- 
moditys  of  places. 

"These  generals  (such  as  at  present  I  could 
think  of),  if  they  will  serve  for  nothing  else,  yet  they 
may  assist  you  in  drawing  up  a  modell  to  regulate 
your  travells  by.  As  for  particulars,  these  that  fol- 
low are  all  that  I  can  now  think  of,  viz.  Whether 
at  Schemnitium,  in  Hungary  (where  there  are  mines 
of  gold,  copper,  iron,  vitrioll,  antimony,  &c.),  they 
change  iron  into  copper  by  dissolving  it  in  a  vitriolate 
water,  which  they  find  in  cavity s  of  rocks  in  the 
mines,  and  then  melting  the  slimy  solution  in  a 
strong  fire,  which  in  the  cooling  proves  copper.  The 
like  is  said  to  be  done  in  other  places,  which  I  can- 
not now  remember ;  perhaps,  too,  it  may  be  done  in 
Italy.  For  about  twenty  or  thirty  years  agone  there 
was  a  certain  vitrioll  came  from  thence  (called 
Roman  vitrioll),  but  of  a  nobler  virtue  than  that 
which  is  now  called  by  that  name ;  which  vitrioll  is 
not  now  to  be  gotten,  because,  perhaps,  they  make 
a  greater  gain  by  some  such  trick  as  turning  iron  into 
copper  with  it  than  by  selling  it.  2.  Whether,  in 
Hungary,  Sclavonia,  Bohemia,  near  the  town  Eila, 
or  at  the  mountains  of  Bohemia  near  Silesia,  there 
be  rivers  whose  waters  are  impregnated  with  gold ; 
perhaps,  the  gold  being  dissolved  by  some  corrosive 


320  APPENDIX. 

waters  like  aqua  regis,  and  the  solution  carried 
along  with  the  streame,  that  runs  through  the  mines. 
And  whether  the  practice  of  laying  mercury  in  the 
rivers,  till  it  be  tinged  with  gold,  and  then  straining 
the  mercury  through  leather,  that  the  gold  may  stay 
behind,  be  a  secret  yet,  or  openly  practised.  3. 
There  is  newly  contrived,  in  Holland,  a  mill  to  grind 
glasses  plane  withall,  and  I  think  polishing  them 
too ;  perhaps  it  will  be  worth  the  while  to  see  it. 

4.  There  is  in  Holland  one Borry,  who  some 

years  since  was  imprisoned  by  the  Pope,  to  have 
extorted  from  him  secrets  (as  I  am  told)  of  great 
worth,  both  as  to  medicine  and  profit,  but  he  escaped 
into  Holland,  where  they  have  granted  him  a  guard. 
J  think  he  usually  goes  clothed  in  green.  Pray  in- 
quire what  you  can  of  him,  and  whether  his  ingenuity 
be  any  profit  to  the  Dutch.  You  may  inform  your- 
self whether  the  Dutch  have  any  tricks  to  keep  their 
ships  from  being  all  worm-eaten  in  their  voyages  to 
the  Indies.  Whether  pendulum  clocks  do  any  ser- 
vice in  finding  out  the  longitude,  &c. 

"  I  am  very  weary,  and  shall  not  stay  to  part  with 
a  long  compliment,  only  I  wish  you  a  good  journey, 
and  God  be  with  you. 

"Is.  NEWTON. 

"  Pray  let  us  hear  from  yon  in  your  travells.  1 
have  given  your  two  books  to  Dr.  Arrowsmith  " 


No.  III. 

A  REMARKABLE    AND    CURIOUS   CONVERSATION    BETWEEN 
SIR  ISAAC  NEWTON  AND  MR.  CONDUIT." 

"  I  WAS  on  Sunday  night,  the  7th  of  March,  1724-5, 
at  Kensington  with  Sir  Isa&v,  Newton,  in  his  lodgings, 
just  after  he  was  come  out  of  a  fit  of  the  gout, 
which  he  had  had  in  both  his  feet,  for  the  first  time, 


APPENDIX.  321 

in  the  eighty-third  year  of  his  age.  He  was  better 
after  it,  and  his  head  clearer,  and  memory  stronger 
than  I  had  known  them  for  some  time.  He  then 
repeated  to  me,  by  way  of  discourse,  very  distinctly, 
though  rather  in  answer  to  my  queries  than  in  one 
continued  narration,  what  he  had  often  hinted  to 
me  before,  viz.  that  it  was  his  conjecture  (he  would 
affirm  nothing)  that  there  was  a  sort  of  revolution 
in  the  heavenly  bodies ;  that  the  vapours  and  light 
emitted  by  the  sun,  which  had  their  sediment  as 
water  and  other  matter,  had  gathered  themselves 
by  degrees  into  a  body,  and  attracted  more  matter 
from  the  planets,  and  at  last  made  a  secondary 
planet  (viz.  one  of  those  that  go  round  another 
planet  and  then  by  gathering  to  them,  and  attract- 
ing more  matter,  became  a  primary  planet ;  and 
then  by  increasing  still  became  a  comet,  which  after 
certain  revolutions,  by  coming  nearer  and  nearer  to 
the  sun,  had  all  its  volatile  parts  condensed,  and 
became  a  matter  fit  to  recruit  and  replenish  the  sun 
(which  must  waste  by  the  constant  heat  and  light 
it  emitted)  as  a  fagot  would  this  fire  if  put  into  it 
I  (we  were  sitting  by  a  wood  fire),  and  that  that 
would  probably  be  the  effect  of  the  comet  of  1680, 
sooner  or  later,  for,  by  the  observations  made  upon 
it,  it  appeared,  before  it  came  near  the  sun,  with 
a  tail  only  two  or  three  degrees  long ;  but  by  the 
heat  it  contracted  in  going  so  near  the  sun,  it 
seemed  to  have  a  tail  of  thirty  or  forty  degrees 
when  it  went  from  it ;  that  he  could  not  say  when 
this  comet  would  drop  into  the  sun ;  it  might  perhaps 
have  five  or  six  revolutions  more  first,  but  whenever 
it  did  it  would  so  much  increase  the  heat  of  the  sun 
that  this  earth  would  be  burnt,  and  no  animals  in  it 
could  live.  That  he  took  the  three  phenomena  seen 
by  Hipparchus,  Tycho  Brahe,  and  Kepler's  disciples 
to  have  been  of  this  kind,  for  he  could  not  otherwise 
account  for  an  extraordinary  light  as  those  were, 
appearing  all  at  once  among  the  fixed  stars  (all 


322  APPENDIX. 

which  he  took  to  be  suns  enlightening  other  planets 
as  our  sun  does  ours)  as  big  as  Mercury  or  Venus 
seems  to  us,  and  gradually  diminishing  for  sixteen 
months,  and  then  sinking  into  nothing.  He  seemed 
to  doubt  whether  there  were  not  intelligent  beings 
superior  to  us  who  superintended  these  revolutions 
of  the  heavenly  bodies  by  the  direction  of  the 
Supreme  Being.  He  appeared  also  to  be  very 
clearly  of  opinion  that  the  inhabitants  of  this  world 
were  of  a  short  date,  and  alleged  as  one  reason  for 
that  opinion,  that  all  arts,  as  letters,  ships,  printing, 
needle,  &c.,  were  discovered  within  the  memory  of 
history,  which  could  not  have  happened  if  the  world 
had  been  eternal ;  and  that  there  were  visible  marks 
of  ruin  upon  it  which  could  not  be  effected  by  a 
flood  only.  When  I  asked  him  how  this  earth  could 
have  been  repeopled  if  ever  it  had  undergone  the 
same  fate  it  was  threatened  with  hereafter  by  the 
comet  of  1680,  he  answered,  that  required  the  power 
of  a  Creator.  He  said  he  took  all  the  planets  to  be 
composed  of  the  same  matter  with  this  earth,  viz. 
earth,  water,  stones,  &c.,  but  variously  concocted. 
I  asked  him  why  he  would  not  publish  his  conjec- 
tures as  conjectures,  and  instanced  that  Kepler  had 
communicated  his ;  and  though  he  had  not  gone 
near  so  far  as  Kepler,  y^i  Kepler's  guesses  were  so 
just  and  happy  that  they  uad  been  proved  and 
demonstrated  by  him.  His  answer  was, '  I  do  not 
deal  in  conjectures.'  But  upon  my  talking  to  him 
about  the  four  observations  that  had  been  made  of 
the  comet  of  1680,  at  574  years'  distance,  and  asking 
him  the  particular  times,  he  opened  his  Principia, 
which  laid  on  the  table,  and  showed  me  there  the 
particular  periods,  viz.  1st,  the  Julium  Sidus,  in  the 
time  of  Justinian,  in  1106,  in  1680. 

And  I,  observing  that  he  said  there  of  that  comet, 
'incidet  in  corpus  solis,'  and  in  the  next  paragraphs 
adds,  '  stellae  fixae  refici  possunt,'  told  him  I  thought 
he  owned  there  what  we  had  been  talking  about, 


APPENDIX.  323 

that  the  comet  would  drop  into  the  sun,  and  that  fixed 
stars  were  recruited  and  replenished  by  comets 
when  they  dropped  into  them ;  and,  consequently, 
that  the  sun  would  be  recruited  too  ;  and  asked  him 
why  he  would  not  own  as  freely  what  he  thought  of 
the  sun  as  well  as  what  he  thought  of  the  fixed  stars. 
He  said,  *  that  concerned  us  more ;'  and,  laughing, 
added, 4  that  he  had  said  enough  for  people  to  know 
his  meaning.' n 

The  preceding  paper,  with  the  title  prefixed  to  it, 
was  first  published  by  Mr.  Turner  in  his  Collections, 

c.  p.  172.  It  was  found  among  the  Portsmouth 
•aanuscripts,  in  the  handwriting  of  Mr.  Conduit. 


THE   ElfH. 


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